Updated UI tests for Light Switch to match new UI

.github/actions/spell-check/expect.txt

@@ -3,6 +3,7 @@ abcdefghjkmnpqrstuvxyz
 abgr
 ABlocked
 ABOUTBOX
+ABORTIFHUNG
 Abug
 Acceleratorkeys
 ACCEPTFILES
@@ -77,6 +78,7 @@ appwiz
 appxpackage
 APSTUDIO
 AQS
+Aquadrant
 ARandom
 ARCHITEW
 ARemapped
@@ -454,6 +456,7 @@ encryptor
 ENDSESSION
 ENSUREVISIBLE
 ENTERSIZEMOVE
+ENTRYW
 ENU
 environmentvariables
 EOAC
@@ -571,6 +574,7 @@ GETDESKWALLPAPER
 GETDLGCODE
 GETDPISCALEDSIZE
 getfilesiginforedist
+geolocator
 GETHOTKEY
 GETICON
 GETMINMAXINFO
@@ -826,6 +830,7 @@ lastcodeanalysissucceeded
 LASTEXITCODE
 LAYOUTRTL
 LCh
+lbl
 lcid
 LCIDTo
 lcl
@@ -844,6 +849,7 @@ LIBID
 LIMITSIZE
 LIMITTEXT
 lindex
+lightswitch
 linkid
 LINKOVERLAY
 LINQTo
@@ -867,10 +873,13 @@ logon
 LOGMSG
 LOGPIXELSX
 LOGPIXELSY
+lng
 LOn
+lon
 longdate
 LONGNAMES
 lowlevel
+lquadrant
 LOWORD
 lparam
 LPBITMAPINFOHEADER
@@ -1383,6 +1392,7 @@ quickaccent
 QUNS
 RAII
 RAlt
+RAquadrant
 randi
 rasterization
 Rasterize
@@ -1681,6 +1691,7 @@ Subdomain
 SUBMODULEUPDATE
 subresource
 Superbar
+suntimes
 sut
 svchost
 SVGIn
@@ -1746,6 +1757,7 @@ tgz
 themeresources
 THH
 THICKFRAME
+THEMECHANGED
 THISCOMPONENT
 throughs
 thumbnailhotkey
@@ -1762,6 +1774,7 @@ tkconverters
 tlb
 tlbimp
 tlc
+tmain
 TNP
 TOGGLEEASYMOUSE
 Toolhelp

.pipelines/ESRPSigning_core.json

@@ -133,6 +133,9 @@
             "PowerToys.ImageResizerContextMenu.dll",
             "ImageResizerContextMenuPackage.msix",
 
+            "PowerToys.LightSwitchModuleInterface.dll",
+            "LightSwitchService\\PowerToys.LightSwitchService.exe",
+
             "PowerToys.KeyboardManager.dll",
             "KeyboardManagerEditor\\PowerToys.KeyboardManagerEditor.exe",
             "KeyboardManagerEngine\\PowerToys.KeyboardManagerEngine.exe",

PowerToys.sln

@@ -5,11 +5,13 @@ MinimumVisualStudioVersion = 10.0.40219.1
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "runner", "src\runner\runner.vcxproj", "{9412D5C6-2CF2-4FC2-A601-B55508EA9B27}"
 	ProjectSection(ProjectDependencies) = postProject
 		{031AC72E-FA28-4AB7-B690-6F7B9C28AA73} = {031AC72E-FA28-4AB7-B690-6F7B9C28AA73}
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC} = {08E71C67-6A7E-4CA1-B04E-2FB336410BAC}
 		{0B43679E-EDFA-4DA0-AD30-F4628B308B1B} = {0B43679E-EDFA-4DA0-AD30-F4628B308B1B}
 		{0B593A6C-4143-4337-860E-DB5710FB87DB} = {0B593A6C-4143-4337-860E-DB5710FB87DB}
 		{17DA04DF-E393-4397-9CF0-84DABE11032E} = {17DA04DF-E393-4397-9CF0-84DABE11032E}
 		{217DF501-135C-4E38-BFC8-99D4821032EA} = {217DF501-135C-4E38-BFC8-99D4821032EA}
 		{2BE46397-4DFA-414C-9BD4-41E4BBF8CB34} = {2BE46397-4DFA-414C-9BD4-41E4BBF8CB34}
+		{38177D56-6AD1-4ADF-88C9-2843A7932166} = {38177D56-6AD1-4ADF-88C9-2843A7932166}
 		{48804216-2A0E-4168-A6D8-9CD068D14227} = {48804216-2A0E-4168-A6D8-9CD068D14227}
 		{51920F1F-C28C-4ADF-8660-4238766796C2} = {51920F1F-C28C-4ADF-8660-4238766796C2}
 		{5CCC8468-DEC8-4D36-99D4-5C891BEBD481} = {5CCC8468-DEC8-4D36-99D4-5C891BEBD481}
@@ -793,6 +795,12 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.CmdPal.Ext.Window
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.CmdPal.Ext.UnitTestBase", "src\modules\cmdpal\Tests\Microsoft.CmdPal.Ext.UnitTestsBase\Microsoft.CmdPal.Ext.UnitTestBase.csproj", "{00D8659C-2068-40B6-8B86-759CD6284BBB}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "LightSwitch", "LightSwitch", "{5B201255-53C8-490B-A34F-01F05D48A477}"
+EndProject
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "LightSwitchModuleInterface", "src\modules\LightSwitch\LightSwitchModuleInterface\LightSwitchModuleInterface.vcxproj", "{38177D56-6AD1-4ADF-88C9-2843A7932166}"
+EndProject
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "LightSwitchService", "src\modules\LightSwitch\LightSwitchService\LightSwitchService.vcxproj", "{08E71C67-6A7E-4CA1-B04E-2FB336410BAC}"
+EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Tests", "Tests", "{E11826E1-76DF-42AC-985C-164CC2EE57A1}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ScreenRuler.UITests", "src\modules\MeasureTool\Tests\ScreenRuler.UITests\ScreenRuler.UITests.csproj", "{66C069F8-C548-4CA6-8CDE-239104D68E88}"
@@ -811,6 +819,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.CmdPal.Ext.WebSea
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.CmdPal.Ext.Shell.UnitTests", "src\modules\cmdpal\Tests\Microsoft.CmdPal.Ext.Shell.UnitTests\Microsoft.CmdPal.Ext.Shell.UnitTests.csproj", "{E816D7B4-4688-4ECB-97CC-3D8E798F3833}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Tests", "Tests", "{3DCCD936-D085-4869-A1DE-CA6A64152C94}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "LightSwitch.UITests", "src\modules\LightSwitch\Tests\LightSwitch.UITests\LightSwitch.UITests.csproj", "{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}"
+EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.CmdPal.Ext.ClipboardHistory.UnitTests", "src\modules\cmdpal\Tests\Microsoft.CmdPal.Ext.ClipboardHistory.UnitTests\Microsoft.CmdPal.Ext.ClipboardHistory.UnitTests.csproj", "{4E0FCF69-B06B-D272-76BF-ED3A559B4EDA}"
 EndProject
 Global
@@ -2891,6 +2903,22 @@ Global
 		{00D8659C-2068-40B6-8B86-759CD6284BBB}.Release|ARM64.Build.0 = Release|ARM64
 		{00D8659C-2068-40B6-8B86-759CD6284BBB}.Release|x64.ActiveCfg = Release|x64
 		{00D8659C-2068-40B6-8B86-759CD6284BBB}.Release|x64.Build.0 = Release|x64
+		{38177D56-6AD1-4ADF-88C9-2843A7932166}.Debug|ARM64.ActiveCfg = Debug|ARM64
+		{38177D56-6AD1-4ADF-88C9-2843A7932166}.Debug|ARM64.Build.0 = Debug|ARM64
+		{38177D56-6AD1-4ADF-88C9-2843A7932166}.Debug|x64.ActiveCfg = Debug|x64
+		{38177D56-6AD1-4ADF-88C9-2843A7932166}.Debug|x64.Build.0 = Debug|x64
+		{38177D56-6AD1-4ADF-88C9-2843A7932166}.Release|ARM64.ActiveCfg = Release|ARM64
+		{38177D56-6AD1-4ADF-88C9-2843A7932166}.Release|ARM64.Build.0 = Release|ARM64
+		{38177D56-6AD1-4ADF-88C9-2843A7932166}.Release|x64.ActiveCfg = Release|x64
+		{38177D56-6AD1-4ADF-88C9-2843A7932166}.Release|x64.Build.0 = Release|x64
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC}.Debug|ARM64.ActiveCfg = Debug|ARM64
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC}.Debug|ARM64.Build.0 = Debug|ARM64
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC}.Debug|x64.ActiveCfg = Debug|x64
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC}.Debug|x64.Build.0 = Debug|x64
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC}.Release|ARM64.ActiveCfg = Release|ARM64
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC}.Release|ARM64.Build.0 = Release|ARM64
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC}.Release|x64.ActiveCfg = Release|x64
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC}.Release|x64.Build.0 = Release|x64
 		{66C069F8-C548-4CA6-8CDE-239104D68E88}.Debug|ARM64.ActiveCfg = Debug|ARM64
 		{66C069F8-C548-4CA6-8CDE-239104D68E88}.Debug|ARM64.Build.0 = Debug|ARM64
 		{66C069F8-C548-4CA6-8CDE-239104D68E88}.Debug|x64.ActiveCfg = Debug|x64
@@ -2947,6 +2975,18 @@ Global
 		{E816D7B4-4688-4ECB-97CC-3D8E798F3833}.Release|ARM64.Build.0 = Release|ARM64
 		{E816D7B4-4688-4ECB-97CC-3D8E798F3833}.Release|x64.ActiveCfg = Release|x64
 		{E816D7B4-4688-4ECB-97CC-3D8E798F3833}.Release|x64.Build.0 = Release|x64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Debug|ARM64.ActiveCfg = Debug|ARM64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Debug|ARM64.Build.0 = Debug|ARM64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Debug|ARM64.Deploy.0 = Debug|ARM64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Debug|x64.ActiveCfg = Debug|x64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Debug|x64.Build.0 = Debug|x64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Debug|x64.Deploy.0 = Debug|x64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Release|ARM64.ActiveCfg = Release|ARM64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Release|ARM64.Build.0 = Release|ARM64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Release|ARM64.Deploy.0 = Release|ARM64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Release|x64.ActiveCfg = Release|x64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Release|x64.Build.0 = Release|x64
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F}.Release|x64.Deploy.0 = Release|x64
 		{4E0FCF69-B06B-D272-76BF-ED3A559B4EDA}.Debug|ARM64.ActiveCfg = Debug|ARM64
 		{4E0FCF69-B06B-D272-76BF-ED3A559B4EDA}.Debug|ARM64.Build.0 = Debug|ARM64
 		{4E0FCF69-B06B-D272-76BF-ED3A559B4EDA}.Debug|x64.ActiveCfg = Debug|x64
@@ -3268,6 +3308,9 @@ Global
 		{E816D7AF-4688-4ECB-97CC-3D8E798F3828} = {8EF25507-2575-4ADE-BF7E-D23376903AB8}
 		{E816D7B0-4688-4ECB-97CC-3D8E798F3829} = {8EF25507-2575-4ADE-BF7E-D23376903AB8}
 		{00D8659C-2068-40B6-8B86-759CD6284BBB} = {8EF25507-2575-4ADE-BF7E-D23376903AB8}
+		{5B201255-53C8-490B-A34F-01F05D48A477} = {4574FDD0-F61D-4376-98BF-E5A1262C11EC}
+		{38177D56-6AD1-4ADF-88C9-2843A7932166} = {5B201255-53C8-490B-A34F-01F05D48A477}
+		{08E71C67-6A7E-4CA1-B04E-2FB336410BAC} = {5B201255-53C8-490B-A34F-01F05D48A477}
 		{E11826E1-76DF-42AC-985C-164CC2EE57A1} = {7AC943C9-52E8-44CF-9083-744D8049667B}
 		{66C069F8-C548-4CA6-8CDE-239104D68E88} = {E11826E1-76DF-42AC-985C-164CC2EE57A1}
 		{9605B84E-FAC4-477B-B9EC-0753177EE6A8} = {557C4636-D7E1-4838-A504-7D19B725EE95}
@@ -3277,6 +3320,8 @@ Global
 		{E816D7B3-4688-4ECB-97CC-3D8E798F3832} = {8EF25507-2575-4ADE-BF7E-D23376903AB8}
 		{E816D7B2-4688-4ECB-97CC-3D8E798F3831} = {8EF25507-2575-4ADE-BF7E-D23376903AB8}
 		{E816D7B4-4688-4ECB-97CC-3D8E798F3833} = {8EF25507-2575-4ADE-BF7E-D23376903AB8}
+		{3DCCD936-D085-4869-A1DE-CA6A64152C94} = {5B201255-53C8-490B-A34F-01F05D48A477}
+		{F5333ED7-06D8-4AB3-953A-36D63F08CB6F} = {3DCCD936-D085-4869-A1DE-CA6A64152C94}
 		{4E0FCF69-B06B-D272-76BF-ED3A559B4EDA} = {8EF25507-2575-4ADE-BF7E-D23376903AB8}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution

doc/devdocs/modules/lightswitch.md

@@ -0,0 +1,107 @@
+# Light Switch
+
+[Public Overview – Microsoft Learn](https://learn.microsoft.com/en-us/windows/powertoys/light-switch)
+
+## Quick Links
+
+* [All Issues](https://github.com/microsoft/PowerToys/issues?q=is%3Aissue%20state%3Aopen%20label%3AProduct-LightSwitch)
+* [Bugs](https://github.com/microsoft/PowerToys/issues?q=is%3Aissue%20state%3Aopen%20label%3AProduct-LightSwitch%20label%3AIssue-Bug)
+* [Pull Requests](https://github.com/microsoft/PowerToys/pulls?q=is%3Apr+is%3Aopen+label%3AProduct-LightSwitch)
+
+## Overview
+
+The **Light Switch** module lets users automatically transition between light and dark mode using a timed schedule or a keyboard shortcut.
+
+## Features
+
+* Set custom times to start and stop dark mode.
+* Use geolocation to determine local sunrise and sunset times.
+* Apply offsets in sunrise mode (e.g., 15 minutes before sunset).
+* Quickly toggle between modes with a keyboard shortcut (`Ctrl+Shift+Win+D` by default).
+* Choose whether theme changes apply to:
+
+  * Apps only
+  * System only
+  * Both apps and system
+
+## Architecture
+
+### Main Components
+
+* **Shortcut/Hotkey**
+  Listens for a hotkey event. Calling `onHotkey()` flips the theme flags.
+
+  > **Note:** Using the shortcut overrides the current schedule until the next transition event.
+
+* **LightSwitchService**
+  Reads settings and applies theming. Runs a check every minute to ensure the state is correct.
+
+* **SettingsXAML/LightSwitch**
+  Provides the settings UI for configuring schedules, syncing location, and customizing shortcuts.
+
+* **Settings.UI/ViewModels/LightSwitchViewModel.cs**
+  Handles updates to the settings file and communicates changes to the front end.
+
+* **modules/LightSwitch/Tests**
+  Contains UI tests that verify interactions between the settings UI, system state, and `settings.json`.
+
+### Data Flow
+
+1. User configures settings in the UI (default: manual mode, light mode from 06:00–18:00).
+2. Every minute, the service checks the time.
+
+   * If it’s not a threshold, the service sleeps until the next minute.
+   * If it matches a threshold, the service applies the theme based on settings and returns to sleep.
+3. At **midnight**, when in *Sunrise to Sunset* mode, the service updates daily sunrise and sunset times.
+4. If the machine was asleep during a scheduled event, the service applies the correct settings at the next check.
+
+## User Interface
+
+The module’s settings are exposed in the PowerToys Settings UI. Options include:
+
+* Shortcut customization
+* Mode selection (Manual or Sunrise to Sunset)
+* Manual start/stop times (manual mode only)
+* Automatic sunrise/sunset calculation (location-based)
+* Time offsets (sunrise mode)
+* Target scope (system, apps, or both)
+
+## Development Environment Setup
+
+### Prerequisites
+
+* Visual Studio 2019 or later
+* Windows 10 SDK
+* PowerToys repository cloned from GitHub
+
+### Building and Testing
+
+1. Clone the repo:
+
+   ```sh
+   git clone https://github.com/microsoft/PowerToys.git
+   ```
+2. Initialize submodules:
+
+   ```sh
+   git submodule update --init --recursive
+   ```
+3. Build the solution:
+
+   ```sh
+   msbuild -restore -p:RestorePackagesConfig=true -p:Platform=ARM64 -m PowerToys.sln
+   ```
+
+   > Note: This may take some time.
+4. Set `runner` as the startup project and press **F5**.
+5. Enable Light Switch in PowerToys Settings.
+6. To debug the service:
+
+   * Press `Ctrl+Alt+P` or go to **Debug > Attach to Process**.
+   * Select `LightSwitchService.exe` and click **Attach**.
+   * You can now set breakpoints in the service files.
+7. To debug the Settings UI:
+
+   * Set the startup project to `PowerToys.Settings` and press **F5**.
+   * Note: Light Switch settings will not persist in this mode (they depend on the service executable).
+   * Alternatively, you can attach `PowerToys.Settings.exe` to the debugger while `runner` is running to test the full flow with breakpoints.

installer/PowerToysSetupCustomActionsVNext/CustomAction.cpp

@@ -1283,7 +1283,7 @@ UINT __stdcall TerminateProcessesCA(MSIHANDLE hInstall)
     }
     processes.resize(bytes / sizeof(processes[0]));
 
-    std::array<std::wstring_view, 41> processesToTerminate = {
+    std::array<std::wstring_view, 42> processesToTerminate = {
         L"PowerToys.PowerLauncher.exe",
         L"PowerToys.Settings.exe",
         L"PowerToys.AdvancedPaste.exe",
@@ -1298,6 +1298,7 @@ UINT __stdcall TerminateProcessesCA(MSIHANDLE hInstall)
         L"PowerToys.Hosts.exe",
         L"PowerToys.PowerRename.exe",
         L"PowerToys.ImageResizer.exe",
+        L"PowerToys.LightSwitchService.exe",
         L"PowerToys.GcodeThumbnailProvider.exe",
         L"PowerToys.BgcodeThumbnailProvider.exe",
         L"PowerToys.PdfThumbnailProvider.exe",

installer/PowerToysSetupCustomActionsVNext/PowerToysSetupCustomActionsVNext.vcxproj

@@ -65,6 +65,7 @@
       call cmd /C "copy ""$(ProjectDir)..\PowerToysSetupVNext\Hosts.wxs"" ""$(ProjectDir)..\PowerToysSetupVNext\Hosts.wxs.bk""""
       call cmd /C "copy ""$(ProjectDir)..\PowerToysSetupVNext\ImageResizer.wxs"" ""$(ProjectDir)..\PowerToysSetupVNext\ImageResizer.wxs.bk""""
       call cmd /C "copy ""$(ProjectDir)..\PowerToysSetupVNext\KeyboardManager.wxs"" ""$(ProjectDir)..\PowerToysSetupVNext\KeyboardManager.wxs.bk""""
+      call cmd /C "copy ""$(ProjectDir)..\PowerToysSetupVNext\LightSwitch.wxs"" ""$(ProjectDir)..\PowerToysSetupVNext\LightSwitch.wxs.bk""""
       call cmd /C "copy ""$(ProjectDir)..\PowerToysSetupVNext\MouseWithoutBorders.wxs"" ""$(ProjectDir)..\PowerToysSetupVNext\MouseWithoutBorders.wxs.bk""""
       call cmd /C "copy ""$(ProjectDir)..\PowerToysSetupVNext\NewPlus.wxs"" ""$(ProjectDir)..\PowerToysSetupVNext\NewPlus.wxs.bk""""
       call cmd /C "copy ""$(ProjectDir)..\PowerToysSetupVNext\Peek.wxs"" ""$(ProjectDir)..\PowerToysSetupVNext\Peek.wxs.bk""""

installer/PowerToysSetupVNext/LightSwitch.wxs

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs">
+
+  <?include $(sys.CURRENTDIR)\Common.wxi?>
+
+  <?define LightSwitchFiles=?>
+  <?define LightSwitchFilesPath=$(var.BinDir)\LightSwitchService\?>
+
+  <Fragment>
+    <!-- Light Switch background service -->
+
+    <!-- Create a directory for the service binaries -->
+    <DirectoryRef Id="INSTALLFOLDER">
+      <Directory Id="LightSwitchServiceFolder" Name="LightSwitchService" />
+    </DirectoryRef>
+
+    <!-- File components generated by generateAllFileComponents.ps1 -->
+    <DirectoryRef Id="LightSwitchServiceFolder" FileSource="$(var.LightSwitchFilesPath)">
+      <!-- Generated by generateFileComponents.ps1 -->
+      <!--LightSwitchFiles_Component_Def-->
+    </DirectoryRef>
+
+    <!-- Group to include the service + cleanup on uninstall -->
+    <ComponentGroup Id="LightSwitchComponentGroup">
+
+      <!-- Ensures folder removal on uninstall -->
+      <Component Id="RemoveLightSwitchServiceFolder" Guid="C1E2F2ED-34A2-4EB0-8E17-DC0535F50F9D" Directory="INSTALLFOLDER">
+        <RegistryKey Root="$(var.RegistryScope)" Key="Software\Classes\powertoys\components">
+          <RegistryValue Type="string" Name="RemoveLightSwitchServiceFolder" Value="" KeyPath="yes" />
+        </RegistryKey>
+        <RemoveFolder Id="RemoveFolderLightSwitchServiceFolder" Directory="LightSwitchServiceFolder" On="uninstall" />
+      </Component>
+    </ComponentGroup>
+  </Fragment>
+</Wix>

installer/PowerToysSetupVNext/PowerToysInstallerVNext.wixproj

@@ -41,6 +41,7 @@ call powershell.exe -NonInteractive -executionpolicy Unrestricted -File $(MSBuil
       call move /Y ..\..\..\FileExplorerPreview.wxs.bk ..\..\..\FileExplorerPreview.wxs
       call move /Y ..\..\..\FileLocksmith.wxs.bk ..\..\..\FileLocksmith.wxs
       call move /Y ..\..\..\Hosts.wxs.bk ..\..\..\Hosts.wxs
+      call move /Y ..\..\..\LightSwitch.wxs.bk ..\..\..\LightSwitch.wxs
       call move /Y ..\..\..\ImageResizer.wxs.bk ..\..\..\ImageResizer.wxs
       call move /Y ..\..\..\KeyboardManager.wxs.bk ..\..\..\KeyboardManager.wxs
       call move /Y ..\..\..\MouseWithoutBorders.wxs.bk ..\..\..\MouseWithoutBorders.wxs
@@ -114,6 +115,7 @@ call powershell.exe -NonInteractive -executionpolicy Unrestricted -File $(MSBuil
     <Compile Include="FileLocksmith.wxs" />
     <Compile Include="Hosts.wxs" />
     <Compile Include="ImageResizer.wxs" />
+    <Compile Include="LightSwitch.wxs" />
     <Compile Include="KeyboardManager.wxs" />
     <Compile Include="Peek.wxs" />
     <Compile Include="PowerRename.wxs" />

installer/PowerToysSetupVNext/Product.wxs

@@ -50,6 +50,7 @@
       <ComponentGroupRef Id="HostsComponentGroup" />
       <ComponentGroupRef Id="ImageResizerComponentGroup" />
       <ComponentGroupRef Id="KeyboardManagerComponentGroup" />
+      <ComponentGroupRef Id="LightSwitchComponentGroup" />
       <ComponentGroupRef Id="PeekComponentGroup" />
       <ComponentGroupRef Id="PowerRenameComponentGroup" />
       <ComponentGroupRef Id="RegistryPreviewComponentGroup" />

installer/PowerToysSetupVNext/generateAllFileComponents.ps1

@@ -182,6 +182,10 @@ Generate-FileComponents -fileListName "HostsAssetsFiles" -wxsFilePath $PSScriptR
 Generate-FileList -fileDepsJson "" -fileListName ImageResizerAssetsFiles -wxsFilePath $PSScriptRoot\ImageResizer.wxs -depsPath "$PSScriptRoot..\..\..\$platform\Release\WinUI3Apps\Assets\ImageResizer"
 Generate-FileComponents -fileListName "ImageResizerAssetsFiles" -wxsFilePath $PSScriptRoot\ImageResizer.wxs -regroot $registryroot
 
+# Light Switch Service
+Generate-FileList -fileDepsJson "" -fileListName LightSwitchFiles -wxsFilePath $PSScriptRoot\LightSwitch.wxs -depsPath "$PSScriptRoot..\..\..\$platform\Release\LightSwitchService"
+Generate-FileComponents -fileListName "LightSwitchFiles" -wxsFilePath $PSScriptRoot\LightSwitch.wxs -regroot $registryroot
+
 #New+
 Generate-FileList -fileDepsJson "" -fileListName NewPlusAssetsFiles -wxsFilePath $PSScriptRoot\NewPlus.wxs -depsPath "$PSScriptRoot..\..\..\$platform\Release\WinUI3Apps\Assets\NewPlus"
 Generate-FileComponents -fileListName "NewPlusAssetsFiles" -wxsFilePath $PSScriptRoot\NewPlus.wxs -regroot $registryroot

src/common/Common.UI/SettingsDeepLink.cs

@@ -17,6 +17,7 @@ namespace Common.UI
             Awake,
             ColorPicker,
             CmdNotFound,
+            LightSwitch,
             FancyZones,
             FileLocksmith,
             Run,
@@ -60,6 +61,8 @@ namespace Common.UI
                     return "ColorPicker";
                 case SettingsWindow.CmdNotFound:
                     return "CmdNotFound";
+                case SettingsWindow.LightSwitch:
+                    return "LightSwitch";
                 case SettingsWindow.FancyZones:
                     return "FancyZones";
                 case SettingsWindow.FileLocksmith:

src/common/GPOWrapper/GPOWrapper.cpp

@@ -28,6 +28,10 @@ namespace winrt::PowerToys::GPOWrapper::implementation
     {
         return static_cast<GpoRuleConfigured>(powertoys_gpo::getConfiguredCropAndLockEnabledValue());
     }
+    GpoRuleConfigured GPOWrapper::GetConfiguredLightSwitchEnabledValue()
+    {
+        return static_cast<GpoRuleConfigured>(powertoys_gpo::getConfiguredLightSwitchEnabledValue());
+    }
     GpoRuleConfigured GPOWrapper::GetConfiguredFancyZonesEnabledValue()
     {
         return static_cast<GpoRuleConfigured>(powertoys_gpo::getConfiguredFancyZonesEnabledValue());

src/common/GPOWrapper/GPOWrapper.h

@@ -13,6 +13,7 @@ namespace winrt::PowerToys::GPOWrapper::implementation
         static GpoRuleConfigured GetConfiguredCmdPalEnabledValue();
         static GpoRuleConfigured GetConfiguredColorPickerEnabledValue();
         static GpoRuleConfigured GetConfiguredCropAndLockEnabledValue();
+        static GpoRuleConfigured GetConfiguredLightSwitchEnabledValue();
         static GpoRuleConfigured GetConfiguredFancyZonesEnabledValue();
         static GpoRuleConfigured GetConfiguredFileLocksmithEnabledValue();
         static GpoRuleConfigured GetConfiguredSvgPreviewEnabledValue();

src/common/GPOWrapper/GPOWrapper.idl

@@ -17,6 +17,7 @@ namespace PowerToys
             static GpoRuleConfigured GetConfiguredCmdPalEnabledValue();
             static GpoRuleConfigured GetConfiguredColorPickerEnabledValue();
             static GpoRuleConfigured GetConfiguredCropAndLockEnabledValue();
+            static GpoRuleConfigured GetConfiguredLightSwitchEnabledValue();
             static GpoRuleConfigured GetConfiguredFancyZonesEnabledValue();
             static GpoRuleConfigured GetConfiguredFileLocksmithEnabledValue();
             static GpoRuleConfigured GetConfiguredSvgPreviewEnabledValue();

src/common/ManagedCommon/ModuleType.cs

@@ -19,6 +19,7 @@ namespace ManagedCommon
         Hosts,
         ImageResizer,
         KeyboardManager,
+        LightSwitch,
         MouseHighlighter,
         MouseJump,
         MousePointerCrosshairs,

src/common/UITestAutomation/Element/Element.cs

@@ -81,6 +81,14 @@ namespace Microsoft.PowerToys.UITest
             get { return this.windowsElement?.Selected ?? false; }
         }
 
+        /// <summary>
+        /// Gets a value indicating whether the UI element is visible to the user.
+        /// </summary>
+        public bool Displayed
+        {
+            get { return this.windowsElement?.Displayed ?? false; }
+        }
+
         /// <summary>
         /// Gets the Rect of the UI element.
         /// </summary>
@@ -329,7 +337,7 @@ namespace Microsoft.PowerToys.UITest
         /// Send Key of the element.
         /// </summary>
         /// <param name="key">The Key to Send.</param>
-        protected void SendKeys(string key)
+        public void SendKeys(string key)
         {
             PerformAction((actions, windowElement) =>
             {
@@ -369,5 +377,19 @@ namespace Microsoft.PowerToys.UITest
             Assert.IsNotNull(this.windowsElement, $"WindowsElement is null in method SaveToPngFile with parameter: path = {path}");
             this.windowsElement.GetScreenshot().SaveAsFile(path);
         }
+
+        public void EnsureVisible(Element scrollViewer, int maxScrolls = 10)
+        {
+            int count = 0;
+            if (scrollViewer.WindowsElement != null)
+            {
+                while (!this.windowsElement!.Displayed && count < maxScrolls)
+                {
+                    scrollViewer.WindowsElement.SendKeys(OpenQA.Selenium.Keys.PageDown);
+                    Task.Delay(250).Wait();
+                    count++;
+                }
+            }
+        }
     }
 }

src/common/UITestAutomation/ModuleConfigData.cs

@@ -34,6 +34,7 @@ namespace Microsoft.PowerToys.UITest
         PowerRename,
         CommandPalette,
         ScreenRuler,
+        LightSwitch,
     }
 
     /// <summary>
@@ -106,6 +107,7 @@ namespace Microsoft.PowerToys.UITest
                 [PowerToysModule.PowerRename] = new ModuleInfo("PowerToys.PowerRename.exe", "PowerRename", "WinUI3Apps"),
                 [PowerToysModule.CommandPalette] = new ModuleInfo("Microsoft.CmdPal.UI.exe", "PowerToys Command Palette", "WinUI3Apps\\CmdPal"),
                 [PowerToysModule.ScreenRuler] = new ModuleInfo("PowerToys.MeasureToolUI.exe", "PowerToys.ScreenRuler", "WinUI3Apps"),
+                [PowerToysModule.LightSwitch] = new ModuleInfo("PowerToys.LightSwitch.exe", "PowerToys.LightSwitch", "LightSwitchService"),
             };
         }
 

src/common/logger/logger_settings.h

@@ -81,6 +81,7 @@ struct LogSettings
     inline const static std::string workspacesSnapshotToolLoggerName = "workspaces-snapshot-tool";
     inline const static std::wstring workspacesSnapshotToolLogPath = L"workspaces-snapshot-tool-log.log";
     inline const static std::string zoomItLoggerName = "zoom-it";
+    inline const static std::string lightSwitchLoggerName = "light-switch";
     inline const static int retention = 30;
     std::wstring logLevel;
     LogSettings();

src/common/utils/elevation.h

@@ -257,7 +257,9 @@ inline HANDLE run_elevated(const std::wstring& file, const std::wstring& params,
         exec_info.nShow = SW_HIDE;
     }
 
-    return ShellExecuteExW(&exec_info) ? exec_info.hProcess : nullptr;
+    BOOL result = ShellExecuteExW(&exec_info);
+
+    return result  ? exec_info.hProcess : nullptr;
 }
 
 // Run command as non-elevated user, returns true if succeeded, puts the process id into returnPid if returnPid != NULL

src/common/utils/gpo.h

@@ -30,6 +30,7 @@ namespace powertoys_gpo
     const std::wstring POLICY_CONFIGURE_ENABLED_CMD_NOT_FOUND = L"ConfigureEnabledUtilityCmdNotFound";
     const std::wstring POLICY_CONFIGURE_ENABLED_COLOR_PICKER = L"ConfigureEnabledUtilityColorPicker";
     const std::wstring POLICY_CONFIGURE_ENABLED_CROP_AND_LOCK = L"ConfigureEnabledUtilityCropAndLock";
+    const std::wstring POLICY_CONFIGURE_ENABLED_LIGHT_SWITCH = L"ConfigureEnabledUtilityLightSwitch";
     const std::wstring POLICY_CONFIGURE_ENABLED_FANCYZONES = L"ConfigureEnabledUtilityFancyZones";
     const std::wstring POLICY_CONFIGURE_ENABLED_FILE_LOCKSMITH = L"ConfigureEnabledUtilityFileLocksmith";
     const std::wstring POLICY_CONFIGURE_ENABLED_SVG_PREVIEW = L"ConfigureEnabledUtilityFileExplorerSVGPreview";
@@ -295,6 +296,11 @@ namespace powertoys_gpo
         return getUtilityEnabledValue(POLICY_CONFIGURE_ENABLED_CROP_AND_LOCK);
     }
 
+    inline gpo_rule_configured_t getConfiguredLightSwitchEnabledValue()
+    {
+        return getUtilityEnabledValue(POLICY_CONFIGURE_ENABLED_LIGHT_SWITCH);
+    }
+
     inline gpo_rule_configured_t getConfiguredFancyZonesEnabledValue()
     {
         return getUtilityEnabledValue(POLICY_CONFIGURE_ENABLED_FANCYZONES);

src/gpo/assets/PowerToys.admx

@@ -137,6 +137,16 @@
         <decimal value="0" />
       </disabledValue>
     </policy>
+    <policy name="ConfigureEnabledUtilityLightSwitch" class="Both" displayName="$(string.ConfigureEnabledUtilityLightSwitch)" explainText="$(string.ConfigureEnabledUtilityDescription)" key="Software\Policies\PowerToys" valueName="ConfigureEnabledUtilityLightSwitch">
+      <parentCategory ref="PowerToys" />
+      <supportedOn ref="SUPPORTED_POWERTOYS_0_95_0" />
+      <enabledValue>
+        <decimal value="1" />
+      </enabledValue>
+      <disabledValue>
+        <decimal value="0" />
+      </disabledValue>
+    </policy>
     <policy name="ConfigureEnabledUtilityEnvironmentVariables" class="Both" displayName="$(string.ConfigureEnabledUtilityEnvironmentVariables)" explainText="$(string.ConfigureEnabledUtilityDescription)" key="Software\Policies\PowerToys" valueName="ConfigureEnabledUtilityEnvironmentVariables">
       <parentCategory ref="PowerToys" />
       <supportedOn ref="SUPPORTED_POWERTOYS_0_75_0" />

src/gpo/assets/en-US/PowerToys.adml

@@ -245,6 +245,7 @@ If you don't configure this policy, the user will be able to control the setting
       <string id="ConfigureEnabledUtilityCmdNotFound">Command Not Found: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityCmdPal">CmdPal: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityCropAndLock">Crop And Lock: Configure enabled state</string>
+      <string id="ConfigureEnabledUtilityLightSwitch">Light Switch: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityEnvironmentVariables">Environment Variables: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityFancyZones">FancyZones: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityFileLocksmith">File Locksmith: Configure enabled state</string>

src/modules/LightSwitch/LightSwitchModuleInterface/LightSwitchModuleInterface.rc

@@ -0,0 +1,32 @@
+1 VERSIONINFO
+ FILEVERSION 0,1,0,0
+ PRODUCTVERSION 0,1,0,0
+ FILEFLAGSMASK 0x3fL
+#ifdef _DEBUG
+ FILEFLAGS 0x1L
+#else
+ FILEFLAGS 0x0L
+#endif
+ FILEOS 0x40004L
+ FILETYPE 0x2L
+ FILESUBTYPE 0x0L
+BEGIN
+    BLOCK "StringFileInfo"
+    BEGIN
+        BLOCK "040904b0"
+        BEGIN
+            VALUE "CompanyName", "Company Name"
+            VALUE "FileDescription", "Light Switch Module"
+            VALUE "FileVersion", "0.1.0.0"
+            VALUE "InternalName", "Light Switch"
+            VALUE "LegalCopyright", "Copyright (C) 2019 Company Name"
+            VALUE "OriginalFilename", "PowerToys.LightSwitchModuleInterface.dll"
+            VALUE "ProductName", "Light Switch"
+            VALUE "ProductVersion", "0.1.0.0"
+        END
+    END
+    BLOCK "VarFileInfo"
+    BEGIN
+        VALUE "Translation", 0x409, 1200
+    END
+END

src/modules/LightSwitch/LightSwitchModuleInterface/LightSwitchModuleInterface.vcxproj

@@ -0,0 +1,225 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="..\..\..\..\packages\Microsoft.Windows.CppWinRT.2.0.240111.5\build\native\Microsoft.Windows.CppWinRT.props" Condition="Exists('..\..\..\..\packages\Microsoft.Windows.CppWinRT.2.0.240111.5\build\native\Microsoft.Windows.CppWinRT.props')" />
+  <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|x64">
+      <Configuration>Debug</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|x64">
+      <Configuration>Release</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|ARM64">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM64">
+      <Configuration>Release</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
+  </ItemGroup>
+  <PropertyGroup Label="Globals">
+    <VCProjectVersion>15.0</VCProjectVersion>
+    <ProjectGuid>{38177d56-6ad1-4adf-88c9-2843a7932166}</ProjectGuid>
+    <Keyword>Win32Proj</Keyword>
+    <RootNamespace>LightSwitchModuleInterface</RootNamespace>
+    <WindowsTargetPlatformVersion>10.0</WindowsTargetPlatformVersion>
+    <ProjectName>LightSwitchModuleInterface</ProjectName>
+    <TargetName>PowerToys.LightSwitchModuleInterface</TargetName>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <UseDebugLibraries>true</UseDebugLibraries>
+    <PlatformToolset>v142</PlatformToolset>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <UseDebugLibraries>false</UseDebugLibraries>
+    <PlatformToolset>v142</PlatformToolset>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|ARM64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <UseDebugLibraries>true</UseDebugLibraries>
+    <PlatformToolset>v142</PlatformToolset>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|ARM64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <UseDebugLibraries>false</UseDebugLibraries>
+    <PlatformToolset>v142</PlatformToolset>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <ImportGroup Label="ExtensionSettings">
+  </ImportGroup>
+  <ImportGroup Label="Shared">
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
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+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
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+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
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+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Release|ARM64'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <PropertyGroup Label="UserMacros" />
+  <PropertyGroup>
+    <OutDir>..\..\..\..\$(Platform)\$(Configuration)\</OutDir>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <LinkIncremental>true</LinkIncremental>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <LinkIncremental>false</LinkIncremental>
+  </PropertyGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <ClCompile>
+      <PrecompiledHeader>Use</PrecompiledHeader>
+      <WarningLevel>Level3</WarningLevel>
+      <Optimization>Disabled</Optimization>
+      <SDLCheck>true</SDLCheck>
+      <PreprocessorDefinitions>_DEBUG;EXAMPLEPOWERTOY_EXPORTS;_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <ConformanceMode>true</ConformanceMode>
+      <PrecompiledHeaderFile>pch.h</PrecompiledHeaderFile>
+      <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
+      <LanguageStandard>stdcpplatest</LanguageStandard>
+    </ClCompile>
+    <Link>
+      <SubSystem>Windows</SubSystem>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <OutputFile>$(OutDir)$(TargetName)$(TargetExt)</OutputFile>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <ClCompile>
+      <PrecompiledHeader>Use</PrecompiledHeader>
+      <WarningLevel>Level3</WarningLevel>
+      <Optimization>MaxSpeed</Optimization>
+      <FunctionLevelLinking>true</FunctionLevelLinking>
+      <IntrinsicFunctions>true</IntrinsicFunctions>
+      <SDLCheck>true</SDLCheck>
+      <PreprocessorDefinitions>NDEBUG;EXAMPLEPOWERTOY_EXPORTS;_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <ConformanceMode>true</ConformanceMode>
+      <PrecompiledHeaderFile>pch.h</PrecompiledHeaderFile>
+      <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
+      <LanguageStandard>stdcpplatest</LanguageStandard>
+    </ClCompile>
+    <Link>
+      <SubSystem>Windows</SubSystem>
+      <EnableCOMDATFolding>true</EnableCOMDATFolding>
+      <OptimizeReferences>true</OptimizeReferences>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <OutputFile>$(OutDir)$(TargetName)$(TargetExt)</OutputFile>
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+    <ClCompile>
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+      <WarningLevel>Level3</WarningLevel>
+      <Optimization>Disabled</Optimization>
+      <SDLCheck>true</SDLCheck>
+      <PreprocessorDefinitions>_DEBUG;EXAMPLEPOWERTOY_EXPORTS;_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <ConformanceMode>true</ConformanceMode>
+      <PrecompiledHeaderFile>pch.h</PrecompiledHeaderFile>
+      <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
+      <LanguageStandard>stdcpplatest</LanguageStandard>
+      <PrecompiledHeader>Use</PrecompiledHeader>
+      <PrecompiledHeaderFile>pch.h</PrecompiledHeaderFile>
+    </ClCompile>
+    <Link>
+      <SubSystem>Windows</SubSystem>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
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+    <ClCompile>
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+      <WarningLevel>Level3</WarningLevel>
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+      <ConformanceMode>true</ConformanceMode>
+      <PrecompiledHeaderFile>pch.h</PrecompiledHeaderFile>
+      <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
+      <LanguageStandard>stdcpplatest</LanguageStandard>
+    </ClCompile>
+    <Link>
+      <SubSystem>Windows</SubSystem>
+      <EnableCOMDATFolding>true</EnableCOMDATFolding>
+      <OptimizeReferences>true</OptimizeReferences>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <OutputFile>$(OutDir)$(TargetName)$(TargetExt)</OutputFile>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup>
+    <ClCompile>
+      <AdditionalIncludeDirectories>..\..\..\common\inc;..\..\..\common\Telemetry;..\..\;..\..\..\;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
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+    <Link>
+      <AdditionalDependencies Condition="'$(Configuration)|$(Platform)'=='Debug|ARM64'">$(CoreLibraryDependencies);%(AdditionalDependencies);advapi32.lib</AdditionalDependencies>
+    </Link>
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+    <ClInclude Include="pch.h" />
+    <ClInclude Include="resource.h" />
+    <ClInclude Include="ThemeHelper.h" />
+    <ClInclude Include="trace.h" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="dllmain.cpp" />
+    <ClCompile Include="pch.cpp">
+      <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">Create</PrecompiledHeader>
+      <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Release|x64'">Create</PrecompiledHeader>
+      <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Debug|ARM64'">Create</PrecompiledHeader>
+      <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Release|ARM64'">Create</PrecompiledHeader>
+      <PrecompiledHeaderFile Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">pch.h</PrecompiledHeaderFile>
+      <PrecompiledHeaderFile Condition="'$(Configuration)|$(Platform)'=='Release|x64'">pch.h</PrecompiledHeaderFile>
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+      <PrecompiledHeaderFile Condition="'$(Configuration)|$(Platform)'=='Release|ARM64'">pch.h</PrecompiledHeaderFile>
+    </ClCompile>
+    <ClCompile Include="ThemeHelper.cpp" />
+    <ClCompile Include="trace.cpp" />
+  </ItemGroup>
+  <ItemGroup>
+    <ResourceCompile Include="LightSwitchModuleInterface.rc" />
+  </ItemGroup>
+  <ItemGroup>
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+      <Project>{d9b8fc84-322a-4f9f-bbb9-20915c47ddfd}</Project>
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+  <ItemGroup>
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+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
+  <Import Project="..\..\..\..\deps\spdlog.props" />
+  <ImportGroup Label="ExtensionTargets">
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+  </ImportGroup>
+  <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
+    <PropertyGroup>
+      <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
+    </PropertyGroup>
+    <Error Condition="!Exists('..\..\..\..\packages\Microsoft.Windows.CppWinRT.2.0.240111.5\build\native\Microsoft.Windows.CppWinRT.props')" Text="$([System.String]::Format('$(ErrorText)', '..\..\..\..\packages\Microsoft.Windows.CppWinRT.2.0.240111.5\build\native\Microsoft.Windows.CppWinRT.props'))" />
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+  </Target>
+</Project>

src/modules/LightSwitch/LightSwitchModuleInterface/LightSwitchModuleInterface.vcxproj.filters

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup>
+    <ClCompile Include="dllmain.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="pch.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="trace.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="ThemeHelper.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="pch.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="resource.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="trace.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="ThemeHelper.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+  </ItemGroup>
+  <ItemGroup>
+    <Filter Include="Header Files">
+      <UniqueIdentifier>{bbf22ac8-46f8-4206-b44b-9c3897e99ce5}</UniqueIdentifier>
+    </Filter>
+    <Filter Include="Source Files">
+      <UniqueIdentifier>{530ed784-9a70-46a0-8fb6-20d5dee4f7d3}</UniqueIdentifier>
+    </Filter>
+    <Filter Include="Resource Files">
+      <UniqueIdentifier>{da1cb871-86d3-414c-adf5-a7e9f2077d2f}</UniqueIdentifier>
+    </Filter>
+  </ItemGroup>
+  <ItemGroup>
+    <ResourceCompile Include="LightSwitchModuleInterface.rc">
+      <Filter>Resource Files</Filter>
+    </ResourceCompile>
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="packages.config" />
+  </ItemGroup>
+</Project>

src/modules/LightSwitch/LightSwitchModuleInterface/ThemeHelper.cpp

@@ -0,0 +1,81 @@
+#include "pch.h"
+#include <windows.h>
+#include "ThemeHelper.h"
+
+// Controls changing the themes.
+
+void SetAppsTheme(bool mode)
+{
+    HKEY hKey;
+    if (RegOpenKeyEx(HKEY_CURRENT_USER,
+                     L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+                     0,
+                     KEY_SET_VALUE,
+                     &hKey) == ERROR_SUCCESS)
+    {
+        DWORD value = mode;
+        RegSetValueEx(hKey, L"AppsUseLightTheme", 0, REG_DWORD, reinterpret_cast<const BYTE*>(&value), sizeof(value));
+        RegCloseKey(hKey);
+
+        SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 0, reinterpret_cast<LPARAM>(L"ImmersiveColorSet"), SMTO_ABORTIFHUNG, 5000, nullptr);
+
+        SendMessageTimeout(HWND_BROADCAST, WM_THEMECHANGED, 0, 0, SMTO_ABORTIFHUNG, 5000, nullptr);
+    }
+}
+
+void SetSystemTheme(bool mode)
+{
+    HKEY hKey;
+    if (RegOpenKeyEx(HKEY_CURRENT_USER,
+                     L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+                     0,
+                     KEY_SET_VALUE,
+                     &hKey) == ERROR_SUCCESS)
+    {
+        DWORD value = mode;
+        RegSetValueEx(hKey, L"SystemUsesLightTheme", 0, REG_DWORD, reinterpret_cast<const BYTE*>(&value), sizeof(value));
+        RegCloseKey(hKey);
+
+        SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 0, reinterpret_cast<LPARAM>(L"ImmersiveColorSet"), SMTO_ABORTIFHUNG, 5000, nullptr);
+
+        SendMessageTimeout(HWND_BROADCAST, WM_THEMECHANGED, 0, 0, SMTO_ABORTIFHUNG, 5000, nullptr);
+    }
+}
+
+bool GetCurrentSystemTheme()
+{
+    HKEY hKey;
+    DWORD value = 1; // default = light
+    DWORD size = sizeof(value);
+
+    if (RegOpenKeyEx(HKEY_CURRENT_USER,
+                     L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+                     0,
+                     KEY_READ,
+                     &hKey) == ERROR_SUCCESS)
+    {
+        RegQueryValueEx(hKey, L"SystemUsesLightTheme", nullptr, nullptr, reinterpret_cast<LPBYTE>(&value), &size);
+        RegCloseKey(hKey);
+    }
+
+    return value == 1; // true = light, false = dark
+}
+
+bool GetCurrentAppsTheme()
+{
+    HKEY hKey;
+    DWORD value = 1;
+    DWORD size = sizeof(value);
+
+    if (RegOpenKeyEx(HKEY_CURRENT_USER,
+                     L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+                     0,
+                     KEY_READ,
+                     &hKey) == ERROR_SUCCESS)
+    {
+        RegQueryValueEx(hKey, L"AppsUseLightTheme", nullptr, nullptr, reinterpret_cast<LPBYTE>(&value), &size);
+        RegCloseKey(hKey);
+    }
+
+    return value == 1; // true = light, false = dark
+}

src/modules/LightSwitch/LightSwitchModuleInterface/ThemeHelper.h

@@ -0,0 +1,5 @@
+#pragma once
+void SetSystemTheme(bool dark);
+void SetAppsTheme(bool dark);
+bool GetCurrentSystemTheme();
+bool GetCurrentAppsTheme();

src/modules/LightSwitch/LightSwitchModuleInterface/dllmain.cpp

@@ -0,0 +1,570 @@
+#include "pch.h"
+#include <interface/powertoy_module_interface.h>
+#include "trace.h"
+#include <common/logger/logger.h>
+#include <common/SettingsAPI/settings_objects.h>
+#include <common/SettingsAPI/settings_helpers.h>
+#include <locale>
+#include <codecvt>
+#include <common/utils/logger_helper.h>
+#include "ThemeHelper.h"
+
+extern "C" IMAGE_DOS_HEADER __ImageBase;
+
+namespace
+{
+    const wchar_t JSON_KEY_PROPERTIES[] = L"properties";
+    const wchar_t JSON_KEY_WIN[] = L"win";
+    const wchar_t JSON_KEY_ALT[] = L"alt";
+    const wchar_t JSON_KEY_CTRL[] = L"ctrl";
+    const wchar_t JSON_KEY_SHIFT[] = L"shift";
+    const wchar_t JSON_KEY_CODE[] = L"code";
+    const wchar_t JSON_KEY_TOGGLE_THEME_HOTKEY[] = L"toggle-theme-hotkey";
+    const wchar_t JSON_KEY_VALUE[] = L"value";
+}
+
+BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved)
+{
+    switch (ul_reason_for_call)
+    {
+    case DLL_PROCESS_ATTACH:
+        Trace::RegisterProvider();
+        break;
+    case DLL_THREAD_ATTACH:
+    case DLL_THREAD_DETACH:
+        break;
+    case DLL_PROCESS_DETACH:
+        Trace::UnregisterProvider();
+        break;
+    }
+    return TRUE;
+}
+
+// The PowerToy name that will be shown in the settings.
+const static wchar_t* MODULE_NAME = L"LightSwitch";
+// Add a description that will we shown in the module settings page.
+const static wchar_t* MODULE_DESC = L"This is a module that allows you to control light/dark theming via set times, sun rise, or directly invoking the change.";
+
+enum class ScheduleMode
+{
+    FixedHours,
+    SunsetToSunrise,
+    // add more later
+};
+
+inline std::wstring ToString(ScheduleMode mode)
+{
+    switch (mode)
+    {
+    case ScheduleMode::SunsetToSunrise:
+        return L"SunsetToSunrise";
+    case ScheduleMode::FixedHours:
+    default:
+        return L"FixedHours";
+    }
+}
+
+inline ScheduleMode FromString(const std::wstring& str)
+{
+    if (str == L"SunsetToSunrise")
+        return ScheduleMode::SunsetToSunrise;
+    return ScheduleMode::FixedHours;
+}
+
+// These are the properties shown in the Settings page.
+struct ModuleSettings
+{
+    bool m_changeSystem = true;
+    bool m_changeApps = true;
+    ScheduleMode m_scheduleMode = ScheduleMode::FixedHours;
+    int m_lightTime = 480;
+    int m_darkTime = 1200;
+    int m_sunrise_offset = 0;
+    int m_sunset_offset = 0;
+    std::wstring m_latitude = L"0.0";
+    std::wstring m_longitude = L"0.0";
+} g_settings;
+
+class LightSwitchInterface : public PowertoyModuleIface
+{
+private:
+    bool m_enabled = false;
+
+    HANDLE m_process{ nullptr };
+    HANDLE m_force_light_event_handle;
+    HANDLE m_force_dark_event_handle;
+    HANDLE m_manual_override_event_handle;
+
+    static const constexpr int NUM_DEFAULT_HOTKEYS = 4;
+
+    Hotkey m_toggle_theme_hotkey = { .win = true, .ctrl = true, .shift = true, .alt = false, .key = 'D' };
+
+    void init_settings();
+
+public:
+    LightSwitchInterface()
+    {
+        LoggerHelpers::init_logger(L"LightSwitch", L"ModuleInterface", LogSettings::lightSwitchLoggerName);
+
+        m_force_light_event_handle = CreateDefaultEvent(L"POWERTOYS_LIGHTSWITCH_FORCE_LIGHT");
+        m_force_dark_event_handle = CreateDefaultEvent(L"POWERTOYS_LIGHTSWITCH_FORCE_DARK");
+        m_manual_override_event_handle = CreateDefaultEvent(L"POWERTOYS_LIGHTSWITCH_MANUAL_OVERRIDE");
+
+        init_settings();
+    };
+
+    virtual const wchar_t* get_key() override
+    {
+        return L"LightSwitch";
+    }
+
+    // Destroy the powertoy and free memory
+    virtual void destroy() override
+    {
+        delete this;
+    }
+
+    // Return the display name of the powertoy, this will be cached by the runner
+    virtual const wchar_t* get_name() override
+    {
+        return MODULE_NAME;
+    }
+
+    // Return the configured status for the gpo policy for the module
+    virtual powertoys_gpo::gpo_rule_configured_t gpo_policy_enabled_configuration() override
+    {
+        return powertoys_gpo::getConfiguredLightSwitchEnabledValue();
+    }
+
+    // Return JSON with the configuration options.
+    virtual bool get_config(wchar_t* buffer, int* buffer_size) override
+    {
+        HINSTANCE hinstance = reinterpret_cast<HINSTANCE>(&__ImageBase);
+
+        // Create a Settings object with your module name
+        PowerToysSettings::Settings settings(hinstance, get_name());
+        settings.set_description(MODULE_DESC);
+        settings.set_overview_link(L"https://aka.ms/powertoys");
+
+        // Boolean toggles
+        settings.add_bool_toggle(
+            L"changeSystem",
+            L"Change System Theme",
+            g_settings.m_changeSystem);
+
+        settings.add_bool_toggle(
+            L"changeApps",
+            L"Change Apps Theme",
+            g_settings.m_changeApps);
+
+        settings.add_choice_group(
+            L"scheduleMode",
+            L"Theme schedule mode",
+            ToString(g_settings.m_scheduleMode),
+            { { L"FixedHours", L"Set hours manually" },
+              { L"SunsetToSunrise", L"Use sunrise/sunset times" } });
+
+        // Integer spinners
+        settings.add_int_spinner(
+            L"lightTime",
+            L"Time to switch to light theme (minutes after midnight).",
+            g_settings.m_lightTime,
+            0,
+            1439,
+            1);
+
+        settings.add_int_spinner(
+            L"darkTime",
+            L"Time to switch to dark theme (minutes after midnight).",
+            g_settings.m_darkTime,
+            0,
+            1439,
+            1);
+
+        settings.add_int_spinner(
+            L"sunrise_offset",
+            L"Time to offset turning on your light theme.",
+            g_settings.m_sunrise_offset,
+            0,
+            1439,
+            1);
+
+        settings.add_int_spinner(
+            L"sunset_offset",
+            L"Time to offset turning on your dark theme.",
+            g_settings.m_sunset_offset,
+            0,
+            1439,
+            1);
+
+        // Strings for latitude and longitude
+        settings.add_string(
+            L"latitude",
+            L"Your latitude in decimal degrees (e.g. 39.95).",
+            g_settings.m_latitude);
+
+        settings.add_string(
+            L"longitude",
+            L"Your longitude in decimal degrees (e.g. -75.16).",
+            g_settings.m_longitude);
+
+        // One-shot actions (buttons)
+        settings.add_custom_action(
+            L"forceLight",
+            L"Switch immediately to light theme",
+            L"Force Light",
+            L"{}");
+
+        settings.add_custom_action(
+            L"forceDark",
+            L"Switch immediately to dark theme",
+            L"Force Dark",
+            L"{}");
+
+        // Hotkeys
+        PowerToysSettings::HotkeyObject dm_hk = PowerToysSettings::HotkeyObject::from_settings(
+            m_toggle_theme_hotkey.win,
+            m_toggle_theme_hotkey.ctrl,
+            m_toggle_theme_hotkey.alt,
+            m_toggle_theme_hotkey.shift,
+            m_toggle_theme_hotkey.key);
+
+        settings.add_hotkey(
+            L"toggle-theme-hotkey",
+            L"Shortcut to toggle theme immediately",
+            dm_hk);
+
+        // Serialize to buffer for the PowerToys runner
+        return settings.serialize_to_buffer(buffer, buffer_size);
+    }
+
+    // Signal from the Settings editor to call a custom action.
+    // This can be used to spawn more complex editors.
+    void call_custom_action(const wchar_t* action) override
+    {
+        try
+        {
+            auto action_object = PowerToysSettings::CustomActionObject::from_json_string(action);
+
+            if (action_object.get_name() == L"forceLight")
+            {
+                Logger::info(L"[Light Switch] Custom action triggered: Force Light");
+                SetSystemTheme(true);
+                SetAppsTheme(true);
+            }
+            else if (action_object.get_name() == L"forceDark")
+            {
+                Logger::info(L"[Light Switch] Custom action triggered: Force Dark");
+                SetSystemTheme(false);
+                SetAppsTheme(false);
+            }
+        }
+        catch (...)
+        {
+            Logger::error(L"[Light Switch] Invalid custom action JSON");
+        }
+    }
+
+    // Called by the runner to pass the updated settings values as a serialized JSON.
+    virtual void set_config(const wchar_t* config) override
+    {
+        try
+        {
+            auto values = PowerToysSettings::PowerToyValues::from_json_string(config, get_key());
+
+            parse_hotkey(values);
+
+            if (auto v = values.get_bool_value(L"changeSystem"))
+            {
+                g_settings.m_changeSystem = *v;
+            }
+
+            if (auto v = values.get_bool_value(L"changeApps"))
+            {
+                g_settings.m_changeApps = *v;
+            }
+
+            if (auto v = values.get_string_value(L"scheduleMode"))
+            {
+                g_settings.m_scheduleMode = FromString(*v);
+            }
+
+            if (auto v = values.get_int_value(L"lightTime"))
+            {
+                g_settings.m_lightTime = *v;
+            }
+
+            if (auto v = values.get_int_value(L"darkTime"))
+            {
+                g_settings.m_darkTime = *v;
+            }
+
+            if (auto v = values.get_int_value(L"sunrise_offset"))
+            {
+                g_settings.m_sunrise_offset = *v;
+            }
+
+            if (auto v = values.get_int_value(L"m_sunset_offset"))
+            {
+                g_settings.m_sunset_offset = *v;
+            }
+
+            if (auto v = values.get_string_value(L"latitude"))
+            {
+                g_settings.m_latitude = *v;
+            }
+            if (auto v = values.get_string_value(L"longitude"))
+            {
+                g_settings.m_longitude = *v;
+            }
+
+            values.save_to_settings_file();
+        }
+        catch (const std::exception&)
+        {
+            Logger::error("[Light Switch] set_config: Failed to parse or apply config.");
+        }
+    }
+
+    virtual void enable()
+    {
+        m_enabled = true;
+        Logger::info(L"Enabling Light Switch module...");
+
+        unsigned long powertoys_pid = GetCurrentProcessId();
+        std::wstring args = L"--pid " + std::to_wstring(powertoys_pid);
+        std::wstring exe_name = L"LightSwitchService\\PowerToys.LightSwitchService.exe";
+
+        std::wstring resolved_path(MAX_PATH, L'\0');
+        DWORD result = SearchPathW(
+            nullptr,
+            exe_name.c_str(),
+            nullptr,
+            static_cast<DWORD>(resolved_path.size()),
+            resolved_path.data(),
+            nullptr);
+
+        if (result == 0 || result >= resolved_path.size())
+        {
+            Logger::error(
+                L"Failed to locate Light Switch executable named '{}' at location '{}'",
+                exe_name,
+                resolved_path.c_str());
+            return;
+        }
+
+        resolved_path.resize(result);
+        Logger::debug(L"Resolved executable path: {}", resolved_path);
+
+        std::wstring command_line = L"\"" + resolved_path + L"\" " + args;
+
+        STARTUPINFO si = { sizeof(si) };
+        PROCESS_INFORMATION pi;
+
+        if (!CreateProcessW(
+                resolved_path.c_str(),
+                command_line.data(),
+                nullptr,
+                nullptr,
+                TRUE,
+                0,
+                nullptr,
+                nullptr,
+                &si,
+                &pi))
+        {
+            Logger::error(L"Failed to launch Light Switch process. {}", get_last_error_or_default(GetLastError()));
+            return;
+        }
+
+        Logger::info(L"Light Switch process launched successfully (PID: {}).", pi.dwProcessId);
+        m_process = pi.hProcess;
+        CloseHandle(pi.hThread);
+    }
+
+    // Disable the powertoy
+    virtual void disable()
+    {
+        Logger::info("Light Switch disabling");
+        m_enabled = false;
+
+        if (m_process)
+        {
+            constexpr DWORD timeout_ms = 1500;
+            DWORD result = WaitForSingleObject(m_process, timeout_ms);
+
+            if (result == WAIT_TIMEOUT)
+            {
+                Logger::warn("Light Switch: Process didn't exit in time. Forcing termination.");
+                TerminateProcess(m_process, 0);
+            }
+
+            CloseHandle(m_manual_override_event_handle);
+            m_manual_override_event_handle = nullptr;
+
+            CloseHandle(m_process);
+            m_process = nullptr;
+        }
+    }
+
+    // Returns if the powertoys is enabled
+    virtual bool is_enabled() override
+    {
+        return m_enabled;
+    }
+
+    void parse_hotkey(PowerToysSettings::PowerToyValues& settings)
+    {
+        auto settingsObject = settings.get_raw_json();
+        if (settingsObject.GetView().Size())
+        {
+            try
+            {
+                Hotkey _temp_toggle_theme;
+                auto jsonHotkeyObject = settingsObject.GetNamedObject(JSON_KEY_PROPERTIES).GetNamedObject(JSON_KEY_TOGGLE_THEME_HOTKEY).GetNamedObject(JSON_KEY_VALUE);
+                _temp_toggle_theme.win = jsonHotkeyObject.GetNamedBoolean(JSON_KEY_WIN);
+                _temp_toggle_theme.alt = jsonHotkeyObject.GetNamedBoolean(JSON_KEY_ALT);
+                _temp_toggle_theme.shift = jsonHotkeyObject.GetNamedBoolean(JSON_KEY_SHIFT);
+                _temp_toggle_theme.ctrl = jsonHotkeyObject.GetNamedBoolean(JSON_KEY_CTRL);
+                _temp_toggle_theme.key = static_cast<unsigned char>(jsonHotkeyObject.GetNamedNumber(JSON_KEY_CODE));
+                m_toggle_theme_hotkey = _temp_toggle_theme;
+            }
+            catch (...)
+            {
+                Logger::error("Failed to initialize Light Switch force dark mode shortcut from settings. Value will keep unchanged.");
+            }
+        }
+        else
+        {
+            Logger::info("Light Switch settings are empty");
+        }
+    }
+
+    virtual size_t get_hotkeys(Hotkey* hotkeys, size_t buffer_size) override
+    {
+        if (hotkeys && buffer_size >= 1)
+        {
+            hotkeys[0] = m_toggle_theme_hotkey;
+        }
+        return 1;
+    }
+
+    virtual bool on_hotkey(size_t hotkeyId) override
+    {
+        if (m_enabled)
+        {
+            Logger::trace(L"Light Switch hotkey pressed");
+            if (!is_process_running())
+            {
+                enable();
+            }
+            else if (hotkeyId == 0)
+            {
+                // get current will return true if in light mode, otherwise false
+                Logger::info(L"[Light Switch] Hotkey triggered: Toggle Theme");
+                if (g_settings.m_changeSystem)
+                {
+                    SetSystemTheme(!GetCurrentSystemTheme());
+                }
+                if (g_settings.m_changeApps)
+                {
+                    SetAppsTheme(!GetCurrentAppsTheme());
+                }
+
+                if (m_manual_override_event_handle)
+                {
+                    SetEvent(m_manual_override_event_handle);
+                    Logger::debug(L"[Light Switch] Manual override event set");
+                }
+            }
+
+            return true;
+        }
+
+        return false;
+    }
+
+    bool is_process_running()
+    {
+        return WaitForSingleObject(m_process, 0) == WAIT_TIMEOUT;
+    }
+};
+
+std::wstring utf8_to_wstring(const std::string& str)
+{
+    if (str.empty())
+        return std::wstring();
+
+    int size_needed = MultiByteToWideChar(
+        CP_UTF8,
+        0,
+        str.c_str(),
+        static_cast<int>(str.size()),
+        nullptr,
+        0);
+
+    std::wstring wstr(size_needed, 0);
+
+    MultiByteToWideChar(
+        CP_UTF8,
+        0,
+        str.c_str(),
+        static_cast<int>(str.size()),
+        &wstr[0],
+        size_needed);
+
+    return wstr;
+}
+
+// Load the settings file.
+void LightSwitchInterface::init_settings()
+{
+    Logger::info(L"[Light Switch] init_settings: starting to load settings for module");
+
+    try
+    {
+        PowerToysSettings::PowerToyValues settings =
+            PowerToysSettings::PowerToyValues::load_from_settings_file(get_name());
+
+        parse_hotkey(settings);
+
+        if (auto v = settings.get_bool_value(L"changeSystem"))
+            g_settings.m_changeSystem = *v;
+        if (auto v = settings.get_bool_value(L"changeApps"))
+            g_settings.m_changeApps = *v;
+        if (auto v = settings.get_string_value(L"scheduleMode"))
+            g_settings.m_scheduleMode = FromString(*v);
+        if (auto v = settings.get_int_value(L"lightTime"))
+            g_settings.m_lightTime = *v;
+        if (auto v = settings.get_int_value(L"darkTime"))
+            g_settings.m_darkTime = *v;
+        if (auto v = settings.get_int_value(L"sunrise_offset"))
+            g_settings.m_sunrise_offset = *v;
+        if (auto v = settings.get_int_value(L"sunset_offset"))
+            g_settings.m_sunset_offset = *v;
+        if (auto v = settings.get_string_value(L"latitude"))
+            g_settings.m_latitude = *v;
+        if (auto v = settings.get_string_value(L"longitude"))
+            g_settings.m_longitude = *v;
+
+        Logger::info(L"[Light Switch] init_settings: loaded successfully");
+    }
+    catch (const winrt::hresult_error& e)
+    {
+        Logger::error(L"[Light Switch] init_settings: hresult_error 0x{:08X} - {}", e.code(), e.message().c_str());
+    }
+    catch (const std::exception& e)
+    {
+        std::wstring whatStr = utf8_to_wstring(e.what());
+        Logger::error(L"[Light Switch] init_settings: std::exception - {}", whatStr);
+    }
+    catch (...)
+    {
+        Logger::error(L"[Light Switch] init_settings: unknown exception while loading settings");
+    }
+}
+
+extern "C" __declspec(dllexport) PowertoyModuleIface* __cdecl powertoy_create()
+{
+    return new LightSwitchInterface();
+}

src/modules/LightSwitch/LightSwitchModuleInterface/pch.cpp

@@ -0,0 +1,2 @@
+#include "pch.h"
+#pragma comment(lib, "windowsapp")

src/modules/LightSwitch/LightSwitchModuleInterface/pch.h

@@ -0,0 +1,14 @@
+#pragma once
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+#include <common/SettingsAPI/settings_helpers.h>
+#include <common/utils/gpo.h>
+#include <common/utils/winapi_error.h>
+#include <shlwapi.h>
+#include <shellapi.h>
+#include <winrt/Windows.Foundation.h>
+#include <winrt/Windows.System.h>
+#include <winrt/Windows.Globalization.h>
+#include <winrt/Windows.ApplicationModel.h>
+#include <winrt/Windows.ApplicationModel.Core.h>

src/modules/LightSwitch/LightSwitchModuleInterface/trace.cpp

@@ -0,0 +1,30 @@
+#include "pch.h"
+#include "trace.h"
+#include <TraceLoggingProvider.h>
+
+TRACELOGGING_DEFINE_PROVIDER(
+    g_hProvider,
+    "Microsoft.PowerToys",
+    // {38e8889b-9731-53f5-e901-e8a7c1753074}
+    (0x38e8889b, 0x9731, 0x53f5, 0xe9, 0x01, 0xe8, 0xa7, 0xc1, 0x75, 0x30, 0x74),
+    TraceLoggingOptionProjectTelemetry());
+
+void Trace::RegisterProvider()
+{
+    TraceLoggingRegister(g_hProvider);
+}
+
+void Trace::UnregisterProvider()
+{
+    TraceLoggingUnregister(g_hProvider);
+}
+
+void Trace::MyEvent()
+{
+    TraceLoggingWrite(
+        g_hProvider,
+        "PowerToyName_MyEvent",
+        ProjectTelemetryPrivacyDataTag(ProjectTelemetryTag_ProductAndServicePerformance),
+        TraceLoggingBoolean(TRUE, "UTCReplace_AppSessionGuid"),
+        TraceLoggingKeyword(PROJECT_KEYWORD_MEASURE));
+}

src/modules/LightSwitch/LightSwitchModuleInterface/trace.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <windows.h>
+#include <TraceLoggingActivity.h>
+#include <common/telemetry/ProjectTelemetry.h>
+
+TRACELOGGING_DECLARE_PROVIDER(g_hProvider);
+
+class Trace
+{
+public:
+    static void RegisterProvider();
+    static void UnregisterProvider();
+    static void MyEvent();
+};

src/modules/LightSwitch/LightSwitchService/LightSwitchService.cpp

@@ -0,0 +1,295 @@
+#include <windows.h>
+#include <tchar.h>
+#include "ThemeScheduler.h"
+#include "ThemeHelper.h"
+#include <common/SettingsAPI/settings_objects.h>
+#include <common/SettingsAPI/settings_helpers.h>
+#include <stdio.h>
+#include <string>
+#include <LightSwitchSettings.h>
+#include <common/utils/gpo.h>
+
+SERVICE_STATUS g_ServiceStatus = {};
+SERVICE_STATUS_HANDLE g_StatusHandle = nullptr;
+HANDLE g_ServiceStopEvent = nullptr;
+static int g_lastUpdatedDay = -1;
+
+VOID WINAPI ServiceMain(DWORD argc, LPTSTR* argv);
+VOID WINAPI ServiceCtrlHandler(DWORD dwCtrl);
+DWORD WINAPI ServiceWorkerThread(LPVOID lpParam);
+
+// Entry point for the executable
+int _tmain(int argc, TCHAR* argv[])
+{
+    DWORD parentPid = 0;
+    bool debug = false;
+    for (int i = 1; i < argc; ++i)
+    {
+        if (_tcscmp(argv[i], _T("--debug")) == 0)
+            debug = true;
+        else if (_tcscmp(argv[i], _T("--pid")) == 0 && i + 1 < argc)
+            parentPid = _tstoi(argv[++i]);
+    }
+
+    // Try to connect to SCM
+    wchar_t serviceName[] = L"LightSwitchService";
+    SERVICE_TABLE_ENTRYW table[] = { { serviceName, ServiceMain }, { nullptr, nullptr } };
+
+    if (!StartServiceCtrlDispatcherW(table))
+    {
+        DWORD err = GetLastError();
+        if (err == ERROR_FAILED_SERVICE_CONTROLLER_CONNECT) // not launched by SCM
+        {
+            g_ServiceStopEvent = CreateEvent(nullptr, TRUE, FALSE, nullptr);
+            HANDLE hThread = CreateThread(
+                nullptr, 0, ServiceWorkerThread, reinterpret_cast<void*>(static_cast<ULONG_PTR>(parentPid)), 0, nullptr);
+
+            // Wait so the process stays alive
+            WaitForSingleObject(hThread, INFINITE);
+            CloseHandle(hThread);
+            CloseHandle(g_ServiceStopEvent);
+            return 0;
+        }
+        return static_cast<int>(err);
+    }
+
+    return 0;
+}
+
+// Called when the service is launched by Windows
+VOID WINAPI ServiceMain(DWORD, LPTSTR*)
+{
+    g_StatusHandle = RegisterServiceCtrlHandler(_T("LightSwitchService"), ServiceCtrlHandler);
+    if (!g_StatusHandle)
+        return;
+
+    g_ServiceStatus.dwServiceType = SERVICE_WIN32_OWN_PROCESS;
+    g_ServiceStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_SHUTDOWN;
+    g_ServiceStatus.dwCurrentState = SERVICE_START_PENDING;
+    SetServiceStatus(g_StatusHandle, &g_ServiceStatus);
+
+    g_ServiceStopEvent = CreateEvent(nullptr, TRUE, FALSE, nullptr);
+    if (!g_ServiceStopEvent)
+    {
+        g_ServiceStatus.dwCurrentState = SERVICE_STOPPED;
+        g_ServiceStatus.dwWin32ExitCode = GetLastError();
+        SetServiceStatus(g_StatusHandle, &g_ServiceStatus);
+        return;
+    }
+
+    SECURITY_ATTRIBUTES sa{ sizeof(sa) };
+    sa.bInheritHandle = FALSE;
+    sa.lpSecurityDescriptor = nullptr;
+
+    g_ServiceStatus.dwCurrentState = SERVICE_RUNNING;
+    SetServiceStatus(g_StatusHandle, &g_ServiceStatus);
+
+    HANDLE hThread = CreateThread(nullptr, 0, ServiceWorkerThread, nullptr, 0, nullptr);
+    WaitForSingleObject(hThread, INFINITE);
+    CloseHandle(hThread);
+
+    CloseHandle(g_ServiceStopEvent);
+    g_ServiceStatus.dwCurrentState = SERVICE_STOPPED;
+    g_ServiceStatus.dwWin32ExitCode = 0;
+    SetServiceStatus(g_StatusHandle, &g_ServiceStatus);
+}
+
+VOID WINAPI ServiceCtrlHandler(DWORD dwCtrl)
+{
+    switch (dwCtrl)
+    {
+    case SERVICE_CONTROL_STOP:
+        if (g_ServiceStatus.dwCurrentState != SERVICE_RUNNING)
+            break;
+
+        g_ServiceStatus.dwCurrentState = SERVICE_STOP_PENDING;
+        SetServiceStatus(g_StatusHandle, &g_ServiceStatus);
+
+        // Signal the service to stop
+        SetEvent(g_ServiceStopEvent);
+        break;
+
+    default:
+        break;
+    }
+}
+
+static void update_sun_times(auto& settings)
+{
+    double latitude = std::stod(settings.latitude);
+    double longitude = std::stod(settings.longitude);
+
+    SYSTEMTIME st;
+    GetLocalTime(&st);
+
+    SunTimes newTimes = CalculateSunriseSunset(latitude, longitude, st.wYear, st.wMonth, st.wDay);
+
+    int newLightTime = newTimes.sunriseHour * 60 + newTimes.sunriseMinute;
+    int newDarkTime = newTimes.sunsetHour * 60 + newTimes.sunsetMinute;
+
+    auto values = PowerToysSettings::PowerToyValues::load_from_settings_file(L"LightSwitch");
+    values.add_property(L"lightTime", newLightTime);
+    values.add_property(L"darkTime", newDarkTime);
+    values.save_to_settings_file();
+
+    OutputDebugString(L"[LightSwitchService] Updated sun times and saved to config.\n");
+}
+
+DWORD WINAPI ServiceWorkerThread(LPVOID lpParam)
+{
+    DWORD parentPid = static_cast<DWORD>(reinterpret_cast<ULONG_PTR>(lpParam));
+    HANDLE hParent = nullptr;
+    if (parentPid)
+        hParent = OpenProcess(SYNCHRONIZE, FALSE, parentPid);
+
+    OutputDebugString(L"[LightSwitchService] Worker thread starting...\n");
+
+    // Initialize settings system
+    LightSwitchSettings::instance().InitFileWatcher();
+
+    // Open the manual override event created by the module interface
+    HANDLE hManualOverride = OpenEventW(SYNCHRONIZE | EVENT_MODIFY_STATE, FALSE, L"POWERTOYS_LIGHTSWITCH_MANUAL_OVERRIDE");
+
+    auto applyTheme = [](int nowMinutes, int lightMinutes, int darkMinutes, const auto& settings) {
+        bool isLightActive = false;
+
+        if (lightMinutes < darkMinutes)
+        {
+            // Normal case: sunrise < sunset
+            isLightActive = (nowMinutes >= lightMinutes && nowMinutes < darkMinutes);
+        }
+        else
+        {
+            // Wraparound case: e.g. light at 21:00, dark at 06:00
+            isLightActive = (nowMinutes >= lightMinutes || nowMinutes < darkMinutes);
+        }
+
+        bool isSystemCurrentlyLight = GetCurrentSystemTheme();
+        bool isAppsCurrentlyLight = GetCurrentAppsTheme();
+
+        if (isLightActive)
+        {
+            if (settings.changeSystem && !isSystemCurrentlyLight)
+                SetSystemTheme(true);
+            if (settings.changeApps && !isAppsCurrentlyLight)
+                SetAppsTheme(true);
+        }
+        else
+        {
+            if (settings.changeSystem && isSystemCurrentlyLight)
+                SetSystemTheme(false);
+            if (settings.changeApps && isAppsCurrentlyLight)
+                SetAppsTheme(false);
+        }
+    };
+
+    // --- At service start: immediately honor the schedule ---
+    {
+        SYSTEMTIME st;
+        GetLocalTime(&st);
+        int nowMinutes = st.wHour * 60 + st.wMinute;
+
+        LightSwitchSettings::instance().LoadSettings();
+        const auto& settings = LightSwitchSettings::instance().settings();
+
+        applyTheme(nowMinutes, settings.lightTime + settings.sunrise_offset, settings.darkTime + settings.sunset_offset, settings);
+    }
+
+    // --- Main loop: wakes once per minute or stop/parent death ---
+    for (;;)
+    {
+        HANDLE waits[2] = { g_ServiceStopEvent, hParent };
+        DWORD count = hParent ? 2 : 1;
+
+        SYSTEMTIME st;
+        GetLocalTime(&st);
+        int nowMinutes = st.wHour * 60 + st.wMinute;
+
+        LightSwitchSettings::instance().LoadSettings();
+        const auto& settings = LightSwitchSettings::instance().settings();
+
+        // Refresh suntimes at day boundary
+        if (g_lastUpdatedDay != st.wDay)
+        {
+            update_sun_times(settings);
+            g_lastUpdatedDay = st.wDay;
+
+            OutputDebugString(L"[LightSwitchService] Recalculated sun times at new day boundary.\n");
+        }
+
+        wchar_t msg[160];
+        swprintf_s(msg,
+                   L"[LightSwitchService] now=%02d:%02d | light=%02d:%02d | dark=%02d:%02d\n",
+                   st.wHour,
+                   st.wMinute,
+                   settings.lightTime / 60,
+                   settings.lightTime % 60,
+                   settings.darkTime / 60,
+                   settings.darkTime % 60);
+        OutputDebugString(msg);
+
+        // --- Manual override check ---
+        bool manualOverrideActive = false;
+        if (hManualOverride)
+        {
+            manualOverrideActive = (WaitForSingleObject(hManualOverride, 0) == WAIT_OBJECT_0);
+        }
+
+        if (manualOverrideActive)
+        {
+            // Did we hit a scheduled boundary? (reset override at boundary)
+            if (nowMinutes == (settings.lightTime + settings.sunrise_offset) % 1440 ||
+                nowMinutes == (settings.darkTime + settings.sunset_offset) % 1440)
+            {
+                ResetEvent(hManualOverride);
+                OutputDebugString(L"[LightSwitchService] Manual override cleared at boundary\n");
+            }
+            else
+            {
+                OutputDebugString(L"[LightSwitchService] Skipping schedule due to manual override\n");
+                goto sleep_until_next_minute;
+            }
+        }
+
+        // Apply theme logic (only runs if no manual override or override just cleared)
+        applyTheme(nowMinutes, settings.lightTime + settings.sunrise_offset, settings.darkTime + settings.sunset_offset, settings);
+
+    sleep_until_next_minute:
+        GetLocalTime(&st);
+        int msToNextMinute = (60 - st.wSecond) * 1000 - st.wMilliseconds;
+        if (msToNextMinute < 50)
+            msToNextMinute = 50;
+
+        DWORD wait = WaitForMultipleObjects(count, waits, FALSE, msToNextMinute);
+        if (wait == WAIT_OBJECT_0) // stop event
+            break;
+        if (hParent && wait == WAIT_OBJECT_0 + 1) // parent exited
+            break;
+    }
+
+    if (hManualOverride)
+        CloseHandle(hManualOverride);
+    if (hParent)
+        CloseHandle(hParent);
+
+    return 0;
+}
+
+int APIENTRY wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)
+{
+    if (powertoys_gpo::getConfiguredLightSwitchEnabledValue() == powertoys_gpo::gpo_rule_configured_disabled)
+    {
+        wchar_t msg[160];
+        swprintf_s(
+            msg,
+            L"Tried to start with a GPO policy setting the utility to always be disabled. Please contact your systems administrator.\n");
+        OutputDebugString(msg);
+        return 0;
+    }
+
+    int argc = 0;
+    LPWSTR* argv = CommandLineToArgvW(GetCommandLineW(), &argc);
+    int rc = _tmain(argc, argv); // reuse your existing logic
+    LocalFree(argv);
+    return rc;
+}

src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj

@@ -0,0 +1,219 @@
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src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj.filters

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+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="ThemeHelper.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="..\..\..\common\SettingsAPI\settings_helpers.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="..\..\..\common\SettingsAPI\settings_objects.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="..\..\..\common\SettingsAPI\FileWatcher.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="LightSwitchSettings.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="SettingsConstants.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="WinHookEventIDs.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="packages.config" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="ThemeScheduler.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="ThemeHelper.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="LightSwitchSettings.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="SettingsConstants.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="SettingsObserver.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="WinHookEventIDs.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+  </ItemGroup>
+  <ItemGroup>
+    <Natvis Include="$(MSBuildThisFileDirectory)..\..\natvis\wil.natvis" />
+  </ItemGroup>
+</Project>

src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.cpp

@@ -0,0 +1,167 @@
+#include "LightSwitchSettings.h"
+#include <common/utils/json.h>
+#include <common/SettingsAPI/settings_helpers.h>
+#include "SettingsObserver.h"
+
+#include <filesystem>
+#include <fstream>
+#include <WinHookEventIDs.h>
+
+using namespace std;
+
+LightSwitchSettings& LightSwitchSettings::instance()
+{
+    static LightSwitchSettings inst;
+    return inst;
+}
+
+LightSwitchSettings::LightSwitchSettings()
+{
+    LoadSettings();
+}
+
+std::wstring LightSwitchSettings::GetSettingsFileName()
+{
+    return PTSettingsHelper::get_module_save_file_location(L"LightSwitch");
+}
+
+void LightSwitchSettings::InitFileWatcher()
+{
+    const std::wstring& settingsFileName = GetSettingsFileName();
+    m_settingsFileWatcher = std::make_unique<FileWatcher>(settingsFileName, [&]() {
+        PostMessageW(HWND_BROADCAST, WM_PRIV_SETTINGS_CHANGED, NULL, NULL);
+    });
+}
+
+void LightSwitchSettings::AddObserver(SettingsObserver& observer)
+{
+    m_observers.insert(&observer);
+}
+
+void LightSwitchSettings::RemoveObserver(SettingsObserver& observer)
+{
+    m_observers.erase(&observer);
+}
+
+void LightSwitchSettings::NotifyObservers(SettingId id) const
+{
+    for (auto observer : m_observers)
+    {
+        if (observer->WantsToBeNotified(id))
+        {
+            observer->SettingsUpdate(id);
+        }
+    }
+}
+
+void LightSwitchSettings::LoadSettings()
+{
+    try
+    {
+        PowerToysSettings::PowerToyValues values =
+            PowerToysSettings::PowerToyValues::load_from_settings_file(L"LightSwitch");
+
+
+        if (const auto jsonVal = values.get_string_value(L"scheduleMode"))
+        {
+            auto val = *jsonVal;
+            auto newMode = FromString(val);
+            if (m_settings.scheduleMode != newMode)
+            {
+                m_settings.scheduleMode = newMode;
+                NotifyObservers(SettingId::ScheduleMode);
+            }
+        }
+
+        // Latitude
+        if (const auto jsonVal = values.get_string_value(L"latitude"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.latitude != val)
+            {
+                m_settings.latitude = val;
+                NotifyObservers(SettingId::Latitude);
+            }
+        }
+
+        // Longitude
+        if (const auto jsonVal = values.get_string_value(L"longitude"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.longitude != val)
+            {
+                m_settings.longitude = val;
+                NotifyObservers(SettingId::Longitude);
+            }
+        }
+
+        // LightTime
+        if (const auto jsonVal = values.get_int_value(L"lightTime"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.lightTime != val)
+            {
+                m_settings.lightTime = val;
+                NotifyObservers(SettingId::LightTime);
+            }
+        }
+
+        // DarkTime
+        if (const auto jsonVal = values.get_int_value(L"darkTime"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.darkTime != val)
+            {
+                m_settings.darkTime = val;
+                NotifyObservers(SettingId::DarkTime);
+            }
+        }
+
+        // Offset
+        if (const auto jsonVal = values.get_int_value(L"sunrise_offset")) 
+        {
+            auto val = *jsonVal;
+            if (m_settings.sunrise_offset != val)
+            {
+                m_settings.sunrise_offset = val;
+                NotifyObservers(SettingId::Sunrise_Offset);
+            }
+        }
+
+        if (const auto jsonVal = values.get_int_value(L"sunset_offset"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.sunset_offset != val)
+            {
+                m_settings.sunset_offset = val;
+                NotifyObservers(SettingId::Sunset_Offset);
+            }
+        }
+
+        // ChangeSystem
+        if (const auto jsonVal = values.get_bool_value(L"changeSystem"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.changeSystem != val)
+            {
+                m_settings.changeSystem = val;
+                NotifyObservers(SettingId::ChangeSystem);
+            }
+        }
+
+        // ChangeApps
+        if (const auto jsonVal = values.get_bool_value(L"changeApps"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.changeApps != val)
+            {
+                m_settings.changeApps = val;
+                NotifyObservers(SettingId::ChangeApps);
+            }
+        }
+    }
+    catch (...)
+    {
+        // Keeps defaults if load fails
+    }
+}

src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.h

@@ -0,0 +1,88 @@
+#pragma once
+
+#include <unordered_set>
+#include <string>
+#include <vector>
+#include <memory>
+#include <windows.h>
+
+#include <common/SettingsAPI/FileWatcher.h>
+#include <common/SettingsAPI/settings_objects.h>
+#include <SettingsConstants.h>
+
+class SettingsObserver;
+
+enum class ScheduleMode
+{
+    FixedHours,
+    SunsetToSunrise
+    // Add more in the future
+};
+
+inline std::wstring ToString(ScheduleMode mode)
+{
+    switch (mode)
+    {
+    case ScheduleMode::FixedHours:
+        return L"FixedHours";
+    case ScheduleMode::SunsetToSunrise:
+        return L"SunsetToSunrise";
+    default:
+        return L"FixedHours";
+    }
+}
+
+inline ScheduleMode FromString(const std::wstring& str)
+{
+    if (str == L"SunsetToSunrise")
+        return ScheduleMode::SunsetToSunrise;
+    else
+        return ScheduleMode::FixedHours;
+}
+
+struct LightSwitchConfig
+{
+    ScheduleMode scheduleMode = ScheduleMode::FixedHours;
+
+    std::wstring latitude = L"0.0";
+    std::wstring longitude = L"0.0";
+
+    // Stored as minutes since midnight
+    int lightTime = 8 * 60; // 08:00 default
+    int darkTime = 20 * 60; // 20:00 default
+
+    int sunrise_offset = 0;
+    int sunset_offset = 0;
+
+    bool changeSystem = false;
+    bool changeApps = false;
+};
+
+class LightSwitchSettings
+{
+public:
+    static LightSwitchSettings& instance();
+
+    static inline const LightSwitchConfig& settings()
+    {
+        return instance().m_settings;
+    }
+
+    void InitFileWatcher();
+    static std::wstring GetSettingsFileName();
+
+    void AddObserver(SettingsObserver& observer);
+    void RemoveObserver(SettingsObserver& observer);
+
+    void LoadSettings();
+
+private:
+    LightSwitchSettings();
+    ~LightSwitchSettings() = default;
+
+    LightSwitchConfig m_settings;
+    std::unique_ptr<FileWatcher> m_settingsFileWatcher;
+    std::unordered_set<SettingsObserver*> m_observers;
+
+    void NotifyObservers(SettingId id) const;
+};

src/modules/LightSwitch/LightSwitchService/SettingsConstants.cpp

@@ -0,0 +1 @@
+#include "SettingsConstants.h"

src/modules/LightSwitch/LightSwitchService/SettingsConstants.h

@@ -0,0 +1,14 @@
+#pragma once
+
+enum class SettingId
+{
+    ScheduleMode = 0,
+    Latitude,
+    Longitude,
+    LightTime,
+    DarkTime,
+    Sunrise_Offset,
+    Sunset_Offset,
+    ChangeSystem,
+    ChangeApps
+};

src/modules/LightSwitch/LightSwitchService/SettingsObserver.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <unordered_set>
+#include "SettingsConstants.h"
+
+class LightSwitchSettings;
+
+class SettingsObserver
+{
+public:
+    SettingsObserver(std::unordered_set<SettingId> observedSettings) :
+        m_observedSettings(std::move(observedSettings))
+    {
+        LightSwitchSettings::instance().AddObserver(*this);
+    }
+
+    virtual ~SettingsObserver()
+    {
+        LightSwitchSettings::instance().RemoveObserver(*this);
+    }
+
+    // Override this in your class to respond to updates
+    virtual void SettingsUpdate(SettingId type) {}
+
+    bool WantsToBeNotified(SettingId type) const noexcept
+    {
+        return m_observedSettings.contains(type);
+    }
+
+protected:
+    std::unordered_set<SettingId> m_observedSettings;
+};

src/modules/LightSwitch/LightSwitchService/ThemeHelper.cpp

@@ -0,0 +1,81 @@
+#include <windows.h>
+#include "ThemeHelper.h"
+
+// Controls changing the themes.
+
+void SetAppsTheme(bool mode)
+{
+    HKEY hKey;
+    if (RegOpenKeyEx(HKEY_CURRENT_USER,
+                     L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+                     0,
+                     KEY_SET_VALUE,
+                     &hKey) == ERROR_SUCCESS)
+    {
+        DWORD value = mode;
+        RegSetValueEx(hKey, L"AppsUseLightTheme", 0, REG_DWORD, reinterpret_cast<const BYTE*>(&value), sizeof(value));
+        RegCloseKey(hKey);
+
+        SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 0, reinterpret_cast<LPARAM>(L"ImmersiveColorSet"), SMTO_ABORTIFHUNG, 5000, nullptr);
+
+        SendMessageTimeout(HWND_BROADCAST, WM_THEMECHANGED, 0, 0, SMTO_ABORTIFHUNG, 5000, nullptr);
+    }
+}
+
+void SetSystemTheme(bool mode)
+{
+    HKEY hKey;
+    if (RegOpenKeyEx(HKEY_CURRENT_USER,
+                     L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+                     0,
+                     KEY_SET_VALUE,
+                     &hKey) == ERROR_SUCCESS)
+    {
+        DWORD value = mode;
+        RegSetValueEx(hKey, L"SystemUsesLightTheme", 0, REG_DWORD, reinterpret_cast<const BYTE*>(&value), sizeof(value));
+        RegCloseKey(hKey);
+
+        SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 0, reinterpret_cast<LPARAM>(L"ImmersiveColorSet"), SMTO_ABORTIFHUNG, 5000, nullptr);
+
+        SendMessageTimeout(HWND_BROADCAST, WM_THEMECHANGED, 0, 0, SMTO_ABORTIFHUNG, 5000, nullptr);
+    }
+}
+
+// Can think of this as "is the current theme light?"
+bool GetCurrentSystemTheme()
+{
+    HKEY hKey;
+    DWORD value = 1; // default = light
+    DWORD size = sizeof(value);
+
+    if (RegOpenKeyEx(HKEY_CURRENT_USER,
+                     L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+                     0,
+                     KEY_READ,
+                     &hKey) == ERROR_SUCCESS)
+    {
+        RegQueryValueEx(hKey, L"SystemUsesLightTheme", nullptr, nullptr, reinterpret_cast<LPBYTE>(&value), &size);
+        RegCloseKey(hKey);
+    }
+
+    return value == 1; // true = light, false = dark
+}
+
+bool GetCurrentAppsTheme()
+{
+    HKEY hKey;
+    DWORD value = 1;
+    DWORD size = sizeof(value);
+
+    if (RegOpenKeyEx(HKEY_CURRENT_USER,
+                     L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+                     0,
+                     KEY_READ,
+                     &hKey) == ERROR_SUCCESS)
+    {
+        RegQueryValueEx(hKey, L"AppsUseLightTheme", nullptr, nullptr, reinterpret_cast<LPBYTE>(&value), &size);
+        RegCloseKey(hKey);
+    }
+
+    return value == 1; // true = light, false = dark
+}

src/modules/LightSwitch/LightSwitchService/ThemeHelper.h

@@ -0,0 +1,5 @@
+#pragma once
+void SetSystemTheme(bool dark);
+void SetAppsTheme(bool dark);
+bool GetCurrentSystemTheme();
+bool GetCurrentAppsTheme();

src/modules/LightSwitch/LightSwitchService/ThemeScheduler.cpp

@@ -0,0 +1,89 @@
+#include "ThemeScheduler.h"
+#include <utility>
+
+SunTimes CalculateSunriseSunset(double latitude, double longitude, int year, int month, int day)
+{
+    double zenith = 90.833;
+    int N1 = static_cast<int>(floor(275.0 * month / 9.0));
+    int N2 = static_cast<int>(floor((static_cast<double>(month) + 9) / 12.0));
+    int N3 = static_cast<int>(floor((1.0 + floor((year - 4.0 * floor(year / 4.0) + 2.0) / 3.0))));
+    int N = N1 - (N2 * N3) + day - 30;
+
+    auto calcTime = [&](bool sunrise) -> double {
+        double lngHour = longitude / 15.0;
+        double t = sunrise ? N + ((6 - lngHour) / 24) : N + ((18 - lngHour) / 24);
+
+        double M = (0.9856 * t) - 3.289;
+        double L = M + (1.916 * sin(deg2rad(M))) + (0.020 * sin(2 * deg2rad(M))) + 282.634;
+        if (L < 0)
+            L += 360;
+        if (L > 360)
+            L -= 360;
+
+        double RA = rad2deg(atan(0.91764 * tan(deg2rad(L))));
+        if (RA < 0)
+            RA += 360;
+        if (RA > 360)
+            RA -= 360;
+
+        double Lquadrant = floor(L / 90) * 90;
+        double RAquadrant = floor(RA / 90) * 90;
+        RA = RA + (Lquadrant - RAquadrant);
+        RA /= 15;
+
+        double sinDec = 0.39782 * sin(deg2rad(L));
+        double cosDec = cos(asin(sinDec));
+
+        double cosH = (cos(deg2rad(zenith)) - (sinDec * sin(deg2rad(latitude)))) / (cosDec * cos(deg2rad(latitude)));
+        if (cosH > 1 || cosH < -1)
+            return -1;
+
+        double H = sunrise ? 360 - rad2deg(acos(cosH)) : rad2deg(acos(cosH));
+        H /= 15;
+
+        double T = H + RA - (0.06571 * t) - 6.622;
+        double UT = T - lngHour;
+        while (UT < 0)
+            UT += 24;
+        while (UT >= 24)
+            UT -= 24;
+
+        return UT;
+    };
+
+    double riseUT = calcTime(true);
+    double setUT = calcTime(false);
+
+    auto toLocal = [](double UT) {
+        TIME_ZONE_INFORMATION tz;
+        DWORD state = GetTimeZoneInformation(&tz);
+        double totalBias = tz.Bias;
+
+        if (state == TIME_ZONE_ID_DAYLIGHT)
+            totalBias += tz.DaylightBias;
+        else if (state == TIME_ZONE_ID_STANDARD)
+            totalBias += tz.StandardBias;
+
+        double biasHours = -(totalBias / 60.0);
+        double localTime = UT + biasHours;
+
+        while (localTime < 0)
+            localTime += 24;
+        while (localTime >= 24)
+            localTime -= 24;
+
+        int hour = static_cast<int>(localTime);
+        int minute = static_cast<int>((localTime - hour) * 60);
+        return std::pair<int, int>{ hour, minute };
+    };
+
+    auto [riseHour, riseMinute] = toLocal(riseUT);
+    auto [setHour, setMinute] = toLocal(setUT);
+
+    SunTimes result;
+    result.sunriseHour = riseHour;
+    result.sunriseMinute = riseMinute;
+    result.sunsetHour = setHour;
+    result.sunsetMinute = setMinute;
+    return result;
+}

src/modules/LightSwitch/LightSwitchService/ThemeScheduler.h

@@ -0,0 +1,25 @@
+#pragma once
+#include <cmath>
+#include <ctime>
+#include <windows.h>
+
+// Struct to hold calculated sunrise/sunset times
+struct SunTimes
+{
+    int sunriseHour;
+    int sunriseMinute;
+    int sunsetHour;
+    int sunsetMinute;
+};
+
+constexpr double PI = 3.14159265358979323846;
+constexpr double deg2rad(double deg)
+{
+    return deg * PI / 180.0;
+}
+constexpr double rad2deg(double rad)
+{
+    return rad * 180.0 / PI;
+}
+
+SunTimes CalculateSunriseSunset(double latitude, double longitude, int year, int month, int day);

src/modules/LightSwitch/LightSwitchService/WinHookEventIDs.cpp

@@ -0,0 +1,15 @@
+
+#include "WinHookEventIDs.h"
+#include <wtypes.h>
+#include <mutex>
+
+UINT WM_PRIV_SETTINGS_CHANGED = 0;
+
+std::once_flag init_flag;
+
+void InitializeWinhookEventIds()
+{
+    std::call_once(init_flag, [&] {
+        WM_PRIV_SETTINGS_CHANGED = RegisterWindowMessage(L"{11978F7B-221A-4E65-B9A9-693F7D6E4B25}");
+    });
+}

src/modules/LightSwitch/LightSwitchService/WinHookEventIDs.h

@@ -0,0 +1,6 @@
+#pragma once
+#include <Windows.h>
+
+extern UINT WM_PRIV_SETTINGS_CHANGED; // Scheduled when a watched settings file is updated
+
+void InitializeWinhookEventIds();

src/modules/LightSwitch/LightSwitchService/packages.config

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<packages>
+  <package id="Microsoft.Windows.CppWinRT" version="2.0.240111.5" targetFramework="native" />
+  <package id="Microsoft.Windows.ImplementationLibrary" version="1.0.231216.1" targetFramework="native" />
+</packages>

src/modules/LightSwitch/LightSwitchService/resource.h

@@ -0,0 +1,16 @@
+//{{NO_DEPENDENCIES}}
+// Microsoft Visual C++ generated include file.
+// Used by LightSwitchService.rc
+//
+#define IDI_ICON1                       101
+
+// Next default values for new objects
+// 
+#ifdef APSTUDIO_INVOKED
+#ifndef APSTUDIO_READONLY_SYMBOLS
+#define _APS_NEXT_RESOURCE_VALUE        102
+#define _APS_NEXT_COMMAND_VALUE         40001
+#define _APS_NEXT_CONTROL_VALUE         1001
+#define _APS_NEXT_SYMED_VALUE           101
+#endif
+#endif

src/modules/LightSwitch/Tests/LightSwitch.UITests/LightSwitch.UITests.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <Import Project="..\..\..\..\Common.Dotnet.CsWinRT.props" />
+  <PropertyGroup>
+    <RootNamespace>PowerToys.LightSwitch.UITests</RootNamespace>
+    <AssemblyName>LightSwitch.UITests</AssemblyName>
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+    <Nullable>enable</Nullable>
+    <OutputType>Library</OutputType>
+
+    <!-- This is a UI test, so don't run as part of MSBuild -->
+    <RunVSTest>false</RunVSTest>
+  </PropertyGroup>
+  <PropertyGroup>
+    <OutputPath>$(SolutionDir)$(Platform)\$(Configuration)\tests\LightSwitch.UITests\</OutputPath>
+  </PropertyGroup>
+
+  <ItemGroup>
+	  <PackageReference Include="MSTest" />
+	  <ProjectReference Include="..\..\..\..\common\UITestAutomation\UITestAutomation.csproj" />
+  </ItemGroup>
+</Project>

src/modules/LightSwitch/Tests/LightSwitch.UITests/Package.appxmanifest

@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<Package
+  xmlns="http://schemas.microsoft.com/appx/manifest/foundation/windows10"
+  xmlns:mp="http://schemas.microsoft.com/appx/2014/phone/manifest"
+  xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10"
+  xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"
+  IgnorableNamespaces="uap rescap">
+
+  <Identity
+    Name="ad22010c-e33e-4459-848e-a1ed976bfd3b"
+    Publisher="CN=Microsoft Corporation, O=Microsoft Corporation, L=Redmond, S=Washington, C=US"
+    Version="1.0.0.0" />
+
+  <mp:PhoneIdentity PhoneProductId="ad22010c-e33e-4459-848e-a1ed976bfd3b" PhonePublisherId="00000000-0000-0000-0000-000000000000"/>
+
+  <Properties>
+    <DisplayName>LightSwitch.UITests</DisplayName>
+    <PublisherDisplayName>Microsoft</PublisherDisplayName>
+    <Logo>Assets\StoreLogo.png</Logo>
+  </Properties>
+
+  <Dependencies>
+    <TargetDeviceFamily Name="Windows.Universal" MinVersion="10.0.17763.0" MaxVersionTested="10.0.19041.0" />
+    <TargetDeviceFamily Name="Windows.Desktop" MinVersion="10.0.17763.0" MaxVersionTested="10.0.19041.0" />
+  </Dependencies>
+
+  <Resources>
+    <Resource Language="x-generate"/>
+  </Resources>
+
+  <Applications>
+    <Application Id="App"
+      Executable="$targetnametoken$.exe"
+      EntryPoint="$targetentrypoint$">
+      <uap:VisualElements
+        DisplayName="LightSwitch.UITests"
+        Description="LightSwitch.UITests"
+        BackgroundColor="transparent"
+        Square150x150Logo="Assets\Square150x150Logo.png"
+        Square44x44Logo="Assets\Square44x44Logo.png">
+        <uap:DefaultTile Wide310x150Logo="Assets\Wide310x150Logo.png" />
+        <uap:SplashScreen Image="Assets\SplashScreen.png" />
+      </uap:VisualElements>
+    </Application>
+  </Applications>
+
+  <Capabilities>
+    <rescap:Capability Name="runFullTrust" />
+  </Capabilities>
+</Package>

src/modules/LightSwitch/Tests/LightSwitch.UITests/TestGeolocation.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.PowerToys.UITest;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace LightSwitch.UITests
+{
+    [TestClass]
+    public class TestGeolocation : UITestBase
+    {
+        public TestGeolocation()
+            : base(PowerToysModule.PowerToysSettings, WindowSize.Large)
+        {
+        }
+
+        [TestMethod("LightSwitch.Geolocation")]
+        [TestCategory("Location")]
+        public void TestGeolocationUpdate()
+        {
+            TestHelper.InitializeTest(this, "geolocation test");
+            TestHelper.PerformGeolocationTest(this);
+            TestHelper.CleanupTest(this);
+        }
+    }
+}

src/modules/LightSwitch/Tests/LightSwitch.UITests/TestHelper.cs

@@ -0,0 +1,439 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using System.Windows.Forms;
+using Microsoft.PowerToys.UITest;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Microsoft.Win32;
+
+namespace LightSwitch.UITests
+{
+    internal sealed class TestHelper
+    {
+        private static readonly string[] ShortcutSeparators = { " + ", "+", " " };
+
+        /// <summary>
+        /// Performs common test initialization: navigate to settings, enable toggle, verify shortcut
+        /// </summary>
+        /// <param name="testBase">The test base instance</param>
+        /// <param name="testName">Name of the test for assertions</param>
+        /// <returns>The activation keys for the test</returns>
+        public static Key[] InitializeTest(UITestBase testBase, string testName)
+        {
+            LaunchFromSetting(testBase);
+
+            var toggleSwitch = SetLightSwitchToggle(testBase, enable: true);
+            Assert.IsTrue(
+                toggleSwitch.IsOn,
+                $"Light Switch toggle switch should be ON for {testName}");
+
+            var activationKeys = ReadActivationShortcut(testBase);
+            Assert.IsNotNull(activationKeys, "Should be able to read activation shortcut");
+            Assert.IsTrue(activationKeys.Length > 0, "Activation shortcut should contain at least one key");
+
+            return activationKeys;
+        }
+
+        /// <summary>
+        /// Navigate to the Light Switch settings page
+        /// </summary>
+        public static void LaunchFromSetting(UITestBase testBase)
+        {
+            var lightSwitch = testBase.Session.FindAll<NavigationViewItem>(By.AccessibilityId("LightSwitchNavItem"));
+
+            if (lightSwitch.Count == 0)
+            {
+                testBase.Session.Find<NavigationViewItem>(By.AccessibilityId("SystemToolsNavItem"), 5000).Click(msPostAction: 500);
+            }
+
+            testBase.Session.Find<NavigationViewItem>(By.AccessibilityId("LightSwitchNavItem"), 5000).Click(msPostAction: 500);
+        }
+
+        /// <summary>
+        /// Set the Light Switch enable toggle switch to the specified state
+        /// </summary>
+        public static ToggleSwitch SetLightSwitchToggle(UITestBase testBase, bool enable)
+        {
+            var toggleSwitch = testBase.Session.Find<ToggleSwitch>(By.AccessibilityId("Toggle_LightSwitch"), 5000);
+
+            if (toggleSwitch.IsOn != enable)
+            {
+                toggleSwitch.Click(msPreAction: 1000, msPostAction: 2000);
+            }
+
+            if (toggleSwitch.IsOn != enable)
+            {
+                testBase.Session.SendKey(Key.Space, msPreAction: 0, msPostAction: 2000);
+            }
+
+            return toggleSwitch;
+        }
+
+        /// <summary>
+        /// Read the current activation shortcut from the ShortcutControl
+        /// </summary>
+        public static Key[] ReadActivationShortcut(UITestBase testBase)
+        {
+            var shortcutCard = testBase.Session.Find<Element>(By.AccessibilityId("Shortcut_LightSwitch"), 5000);
+            var shortcutButton = shortcutCard.Find<Element>(By.AccessibilityId("EditButton"), 5000);
+            return ParseShortcutText(shortcutButton.HelpText);
+        }
+
+        /// <summary>
+        /// Parse shortcut text like "Win + Ctrl + Shift + M" into Key array
+        /// </summary>
+        private static Key[] ParseShortcutText(string shortcutText)
+        {
+            if (string.IsNullOrEmpty(shortcutText))
+            {
+                return new Key[] { Key.Win, Key.Ctrl, Key.Shift, Key.D };
+            }
+
+            var keys = new List<Key>();
+            var parts = shortcutText.Split(ShortcutSeparators, StringSplitOptions.RemoveEmptyEntries);
+
+            foreach (var part in parts)
+            {
+                var cleanPart = part.Trim().ToLowerInvariant();
+                var key = cleanPart switch
+                {
+                    "win" or "windows" => Key.Win,
+                    "ctrl" or "control" => Key.Ctrl,
+                    "shift" => Key.Shift,
+                    "alt" => Key.Alt,
+                    _ when cleanPart.Length == 1 && char.IsLetter(cleanPart[0]) &&
+                         cleanPart[0] >= 'a' && cleanPart[0] <= 'z' =>
+                        (Key)Enum.Parse(typeof(Key), cleanPart.ToUpperInvariant()),
+                    _ => (Key?)null,
+                };
+
+                if (key.HasValue)
+                {
+                    keys.Add(key.Value);
+                }
+            }
+
+            return keys.Count > 0 ? keys.ToArray() : new Key[] { Key.Win, Key.Ctrl, Key.Shift, Key.D };
+        }
+
+        /// <summary>
+        /// Performs common test cleanup: close LightSwitch task
+        /// </summary>
+        /// <param name="testBase">The test base instance</param>
+        public static void CleanupTest(UITestBase testBase)
+        {
+            // TODO: Make sure the task kills?
+            // CloseLightSwitch(testBase);
+
+            // Ensure we're attached to settings after cleanup
+            try
+            {
+                testBase.Session.Attach(PowerToysModule.PowerToysSettings);
+            }
+            catch
+            {
+                // Ignore attachment errors - this is just cleanup
+            }
+        }
+
+        /// <summary>
+        /// Perform a update time test operation
+        /// </summary>
+        public static void PerformUpdateTimeTest(UITestBase testBase)
+        {
+            // Make sure in manual mode
+            var modeCombobox = testBase.Session.Find<Element>(By.AccessibilityId("ModeSelection_LightSwitch"), 5000);
+            Assert.IsNotNull(modeCombobox, "Mode combobox not found.");
+
+            var neededTabs = 6;
+
+            if (modeCombobox.Text != "Manual")
+            {
+                modeCombobox.Click();
+                var manualListItem = testBase.Session.Find<Element>(By.AccessibilityId("ManualCBItem_LightSwitch"), 5000);
+                Assert.IsNotNull(manualListItem, "Manual combobox item not found.");
+                manualListItem.Click();
+                neededTabs = 1;
+            }
+
+            Assert.AreEqual("Manual", modeCombobox.Text, "Mode combobox should be set to Manual.");
+
+            var timeline = testBase.Session.Find<Element>(By.AccessibilityId("Timeline_LightSwitch"), 5000);
+            Assert.IsNotNull(timeline, "Timeline not found.");
+
+            var helpText = timeline.GetAttribute("HelpText");
+            string originalEndValue = GetHelpTextValue(helpText, "End");
+
+            for (int i = 0; i < neededTabs; i++)
+            {
+                testBase.Session.SendKeys(Key.Tab);
+            }
+
+            testBase.Session.SendKeys(Key.Enter);
+            testBase.Session.SendKeys(Key.Up);
+            testBase.Session.SendKeys(Key.Enter);
+
+            helpText = timeline.GetAttribute("HelpText");
+            string updatedEndValue = GetHelpTextValue(helpText, "End");
+
+            Assert.AreNotEqual(originalEndValue, updatedEndValue, "Timeline end time should have been updated.");
+
+            helpText = timeline.GetAttribute("HelpText");
+            string originalStartValue = GetHelpTextValue(helpText, "Start");
+
+            testBase.Session.SendKeys(Key.Tab);
+            testBase.Session.SendKeys(Key.Enter);
+            testBase.Session.SendKeys(Key.Up);
+            testBase.Session.SendKeys(Key.Enter);
+
+            helpText = timeline.GetAttribute("HelpText");
+            string updatedStartValue = GetHelpTextValue(helpText, "Start");
+
+            Assert.AreNotEqual(originalStartValue, updatedStartValue, "Timeline start time should have been updated.");
+        }
+
+        /// <summary>
+        /// Perform a update geolocation test operation
+        /// </summary>
+        public static void PerformUserSelectedLocationTest(UITestBase testBase)
+        {
+            // Make sure in sun time mode
+            var modeCombobox = testBase.Session.Find<Element>(By.AccessibilityId("ModeSelection_LightSwitch"), 5000);
+            Assert.IsNotNull(modeCombobox, "Mode combobox not found.");
+
+            if (modeCombobox.Text != "Sunset to sunrise")
+            {
+                modeCombobox.Click();
+                var sunriseListItem = testBase.Session.Find<Element>(By.AccessibilityId("SunCBItem_LightSwitch"), 5000);
+                Assert.IsNotNull(sunriseListItem, "Sunrise combobox item not found.");
+                sunriseListItem.Click();
+            }
+
+            Assert.AreEqual("Sunset to sunrise", modeCombobox.Text, "Mode combobox should be set to Sunset to sunrise.");
+
+            var setLocationButton = testBase.Session.Find<Element>(By.AccessibilityId("SetLocationButton_LightSwitch"), 5000);
+            Assert.IsNotNull(setLocationButton, "Set location button not found.");
+            setLocationButton.Click();
+
+            var autoSuggestTextbox = testBase.Session.Find<Element>(By.AccessibilityId("CitySearchBox_LightSwitch"), 5000);
+            Assert.IsNotNull(autoSuggestTextbox, "City search box not found.");
+            autoSuggestTextbox.Click();
+            autoSuggestTextbox.SendKeys("Seattle");
+            autoSuggestTextbox.SendKeys(OpenQA.Selenium.Keys.Down);
+            autoSuggestTextbox.SendKeys(OpenQA.Selenium.Keys.Enter);
+
+            var latLong = testBase.Session.Find<Element>(By.AccessibilityId("LocationResultText_LightSwitch"), 5000);
+            Assert.IsFalse(string.IsNullOrWhiteSpace(latLong.Text));
+
+            var sunrise = testBase.Session.Find<Element>(By.AccessibilityId("SunriseText_LightSwitch"), 5000);
+            Assert.IsFalse(string.IsNullOrWhiteSpace(sunrise.Text));
+
+            var sunset = testBase.Session.Find<Element>(By.AccessibilityId("SunsetText_LightSwitch"), 5000);
+            Assert.IsFalse(string.IsNullOrWhiteSpace(sunset.Text));
+        }
+
+        /// <summary>
+        /// Perform a update geolocation test operation
+        /// </summary>
+        public static void PerformGeolocationTest(UITestBase testBase)
+        {
+            // Make sure in sun time mode
+            var modeCombobox = testBase.Session.Find<Element>(By.AccessibilityId("ModeSelection_LightSwitch"), 5000);
+            Assert.IsNotNull(modeCombobox, "Mode combobox not found.");
+
+            if (modeCombobox.Text != "Sunset to sunrise")
+            {
+                modeCombobox.Click();
+                var sunriseListItem = testBase.Session.Find<Element>(By.AccessibilityId("SunCBItem_LightSwitch"), 5000);
+                Assert.IsNotNull(sunriseListItem, "Sunrise combobox item not found.");
+                sunriseListItem.Click();
+            }
+
+            Assert.AreEqual("Sunset to sunrise", modeCombobox.Text, "Mode combobox should be set to Sunset to sunrise.");
+
+            // Click the select city button
+            var setLocationButton = testBase.Session.Find<Element>(By.AccessibilityId("SetLocationButton_LightSwitch"), 5000);
+            Assert.IsNotNull(setLocationButton, "Set location button not found.");
+            setLocationButton.Click(msPostAction: 8000);
+
+            var latLong = testBase.Session.Find<Element>(By.AccessibilityId("LocationResultText_LightSwitch"), 5000);
+            Assert.IsFalse(string.IsNullOrWhiteSpace(latLong.Text));
+
+            var sunrise = testBase.Session.Find<Element>(By.AccessibilityId("SunriseText_LightSwitch"), 5000);
+            Assert.IsFalse(string.IsNullOrWhiteSpace(sunrise.Text));
+
+            var sunset = testBase.Session.Find<Element>(By.AccessibilityId("SunsetText_LightSwitch"), 5000);
+            Assert.IsFalse(string.IsNullOrWhiteSpace(sunset.Text));
+        }
+
+        /// <summary>
+        /// Perform a update time test operation
+        /// </summary>
+        public static void PerformOffsetTest(UITestBase testBase)
+        {
+            // Make sure in sun time mode
+            var modeCombobox = testBase.Session.Find<Element>(By.AccessibilityId("ModeSelection_LightSwitch"), 5000);
+            Assert.IsNotNull(modeCombobox, "Mode combobox not found.");
+
+            if (modeCombobox.Text != "Sunset to sunrise")
+            {
+                modeCombobox.Click();
+                var sunriseListItem = testBase.Session.Find<Element>(By.AccessibilityId("SunCBItem_LightSwitch"), 5000);
+                Assert.IsNotNull(sunriseListItem, "Sunrise combobox item not found.");
+                sunriseListItem.Click();
+            }
+
+            Assert.AreEqual("Sunset to sunrise", modeCombobox.Text, "Mode combobox should be set to Sunset to sunrise.");
+
+            // Testing sunrise offset
+            var sunriseOffset = testBase.Session.Find<Element>(By.AccessibilityId("SunriseOffset_LightSwitch"), 5000);
+            Assert.IsNotNull(sunriseOffset, "Sunrise offset number box not found.");
+
+            var timeline = testBase.Session.Find<Element>(By.AccessibilityId("Timeline_LightSwitch"), 5000);
+            Assert.IsNotNull(timeline, "Timeline not found.");
+
+            var helpText = timeline.GetAttribute("HelpText");
+            string originalStartValue = GetHelpTextValue(helpText, "Start");
+
+            sunriseOffset.Click();
+            testBase.Session.SendKeys(Key.Up);
+
+            helpText = timeline.GetAttribute("HelpText");
+            string updatedStartValue = GetHelpTextValue(helpText, "Start");
+
+            Assert.AreNotEqual(originalStartValue, updatedStartValue, "Timeline start time should have been updated.");
+
+            // Testing sunset offset
+            var sunsetOffset = testBase.Session.Find<Element>(By.AccessibilityId("SunsetOffset_LightSwitch"), 5000);
+            Assert.IsNotNull(sunsetOffset, "Sunrise offset number box not found.");
+
+            helpText = timeline.GetAttribute("HelpText");
+            string originalEndValue = GetHelpTextValue(helpText, "End");
+
+            sunsetOffset.Click();
+            testBase.Session.SendKeys(Key.Up);
+
+            helpText = timeline.GetAttribute("HelpText");
+            string updatedEndValue = GetHelpTextValue(helpText, "End");
+
+            Assert.AreNotEqual(originalEndValue, updatedEndValue, "Timeline end time should have been updated.");
+        }
+
+        /// <summary>
+        /// Perform a test for shortcut changing themes
+        /// </summary>
+        public static void PerformShortcutTest(UITestBase testBase, Key[] activationKeys)
+        {
+            // Test when both are checked
+            var systemCheckbox = testBase.Session.Find<Element>(By.AccessibilityId("ChangeSystemCheckbox_LightSwitch"), 5000);
+            Assert.IsNotNull(systemCheckbox, "System checkbox not found.");
+
+            var scrollViewer = testBase.Session.Find<Element>(By.AccessibilityId("PageScrollViewer"));
+            systemCheckbox.EnsureVisible(scrollViewer);
+
+            int neededTabs = 10;
+
+            if (!systemCheckbox.Selected)
+            {
+                for (int i = 0; i < neededTabs; i++)
+                {
+                    testBase.Session.SendKeys(Key.Tab);
+                }
+
+                systemCheckbox.Click();
+            }
+
+            Assert.IsTrue(systemCheckbox.Selected, "System checkbox should be checked.");
+
+            var appsCheckbox = testBase.Session.Find<Element>(By.AccessibilityId("ChangeAppsCheckbox_LightSwitch"), 5000);
+            Assert.IsNotNull(appsCheckbox, "Apps checkbox not found.");
+
+            if (!appsCheckbox.Selected)
+            {
+                appsCheckbox.Click();
+            }
+
+            Assert.IsTrue(appsCheckbox.Selected, "Apps checkbox should be checked.");
+
+            var systemBeforeValue = GetSystemTheme();
+            var appsBeforeValue = GetAppsTheme();
+
+            testBase.Session.SendKeys(activationKeys);
+            Task.Delay(5000).Wait();
+
+            var systemAfterValue = GetSystemTheme();
+            var appsAfterValue = GetAppsTheme();
+
+            Assert.AreNotEqual(systemBeforeValue, systemAfterValue, "System theme should have changed.");
+            Assert.AreNotEqual(appsBeforeValue, appsAfterValue, "Apps theme should have changed.");
+
+            // Test with nothing checked
+            if (systemCheckbox.Selected)
+            {
+                systemCheckbox.Click();
+            }
+
+            if (appsCheckbox.Selected)
+            {
+                appsCheckbox.Click();
+            }
+
+            Assert.IsFalse(systemCheckbox.Selected, "System checkbox should be unchecked.");
+            Assert.IsFalse(appsCheckbox.Selected, "Apps checkbox should be unchecked.");
+
+            var noneSystemBeforeValue = GetSystemTheme();
+            var noneAppsBeforeValue = GetAppsTheme();
+
+            testBase.Session.SendKeys(activationKeys);
+            Task.Delay(5000).Wait();
+
+            var noneSystemAfterValue = GetSystemTheme();
+            var noneAppsAfterValue = GetAppsTheme();
+
+            Assert.AreEqual(noneSystemBeforeValue, noneSystemAfterValue, "System theme should not have changed.");
+            Assert.AreEqual(noneAppsBeforeValue, noneAppsAfterValue, "Apps theme should not have changed.");
+        }
+
+        /* Helpers */
+        private static int GetSystemTheme()
+        {
+            using var key = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize");
+            if (key is null)
+            {
+                return 1;
+            }
+
+            return (int)key.GetValue("SystemUsesLightTheme", 1);
+        }
+
+        private static int GetAppsTheme()
+        {
+            using var key = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize");
+            if (key is null)
+            {
+                return 1;
+            }
+
+            return (int)key.GetValue("AppsUseLightTheme", 1);
+        }
+
+        private static string GetHelpTextValue(string helpText, string key)
+        {
+            foreach (var part in helpText.Split(';'))
+            {
+                var kv = part.Split('=');
+                if (kv.Length == 2 && kv[0] == key)
+                {
+                    return kv[1];
+                }
+            }
+
+            return string.Empty;
+        }
+    }
+}

src/modules/LightSwitch/Tests/LightSwitch.UITests/TestOffset.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.PowerToys.UITest;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace LightSwitch.UITests
+{
+    [TestClass]
+    public class TestOffset : UITestBase
+    {
+        public TestOffset()
+            : base(PowerToysModule.PowerToysSettings, WindowSize.Large)
+        {
+        }
+
+        [TestMethod("LightSwitch.Offset")]
+        [TestCategory("Time")]
+        public void TestTimeOffset()
+        {
+            TestHelper.InitializeTest(this, "offset test");
+            TestHelper.PerformOffsetTest(this);
+            TestHelper.CleanupTest(this);
+        }
+    }
+}

src/modules/LightSwitch/Tests/LightSwitch.UITests/TestShortcut.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.PowerToys.UITest;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace LightSwitch.UITests
+{
+    [TestClass]
+    public class TestShortcut : UITestBase
+    {
+        public TestShortcut()
+            : base(PowerToysModule.PowerToysSettings, WindowSize.Large)
+        {
+        }
+
+        [TestMethod("LightSwitch.TestShortcut")]
+        [TestCategory("Shortcut")]
+        public void TestLightSwitchShortcut()
+        {
+            var activationKeys = TestHelper.InitializeTest(this, "light switch shortcut test");
+            TestHelper.PerformShortcutTest(this, activationKeys);
+            TestHelper.CleanupTest(this);
+        }
+    }
+}

src/modules/LightSwitch/Tests/LightSwitch.UITests/TestUpdateManualTime.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.PowerToys.UITest;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace LightSwitch.UITests
+{
+    [TestClass]
+    public class TestUpdateManualTime : UITestBase
+    {
+        public TestUpdateManualTime()
+            : base(PowerToysModule.PowerToysSettings, WindowSize.Large)
+        {
+        }
+
+        [TestMethod("LightSwitch.UpdateManualTime")]
+        [TestCategory("Time")]
+        public void TestUpdateTime()
+        {
+            TestHelper.InitializeTest(this, "update manual time test");
+            TestHelper.PerformUpdateTimeTest(this);
+            TestHelper.CleanupTest(this);
+        }
+    }
+}

src/modules/LightSwitch/Tests/LightSwitch.UITests/app.manifest

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
+  <assemblyIdentity version="1.0.0.0" name="LightSwitch.UITests.app"/>
+
+  <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
+    <application>
+      <!-- The ID below informs the system that this application is compatible with OS features first introduced in Windows 10. 
+      It is necessary to support features in unpackaged applications, for example the custom titlebar implementation.
+      For more info see https://docs.microsoft.com/windows/apps/windows-app-sdk/use-windows-app-sdk-run-time#declare-os-compatibility-in-your-application-manifest -->
+      <supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}" />
+    </application>
+  </compatibility>
+  
+  <application xmlns="urn:schemas-microsoft-com:asm.v3">
+    <windowsSettings>
+      <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2</dpiAwareness>
+    </windowsSettings>
+  </application>
+</assembly>

src/runner/main.cpp

@@ -177,6 +177,7 @@ int runner(bool isProcessElevated, bool openSettings, std::string settingsWindow
             L"PowerToys.WorkspacesModuleInterface.dll",
             L"PowerToys.CmdPalModuleInterface.dll",
             L"PowerToys.ZoomItModuleInterface.dll",
+            L"PowerToys.LightSwitchModuleInterface.dll",
         };
 
         for (auto moduleSubdir : knownModules)

src/runner/settings_window.cpp

@@ -757,6 +757,8 @@ std::string ESettingsWindowNames_to_string(ESettingsWindowNames value)
         return "ColorPicker";
     case ESettingsWindowNames::CmdNotFound:
         return "CmdNotFound";
+    case ESettingsWindowNames::LightSwitch:
+        return "LightSwitch";
     case ESettingsWindowNames::FancyZones:
         return "FancyZones";
     case ESettingsWindowNames::FileLocksmith:
@@ -842,6 +844,10 @@ ESettingsWindowNames ESettingsWindowNames_from_string(std::string value)
     {
         return ESettingsWindowNames::CmdNotFound;
     }
+    else if (value == "LightSwitch")
+    {
+        return ESettingsWindowNames::LightSwitch;
+    }
     else if (value == "FancyZones")
     {
         return ESettingsWindowNames::FancyZones;

src/runner/settings_window.h

@@ -10,6 +10,7 @@ enum class ESettingsWindowNames
     Awake,
     ColorPicker,
     CmdNotFound,
+    LightSwitch,
     FancyZones,
     FileLocksmith,
     Run,

src/settings-ui/Settings.UI.Library/EnabledModules.cs

@@ -513,6 +513,23 @@ namespace Microsoft.PowerToys.Settings.UI.Library
             }
         }
 
+        private bool lightSwitch;
+
+        [JsonPropertyName("LightSwitch")]
+        public bool LightSwitch
+        {
+            get => lightSwitch;
+            set
+            {
+                if (lightSwitch != value)
+                {
+                    LogTelemetryEvent(value);
+                    lightSwitch = value;
+                    NotifyChange();
+                }
+            }
+        }
+
         private void NotifyChange()
         {
             notifyEnabledChangedAction?.Invoke();

src/settings-ui/Settings.UI.Library/Helpers/SearchLocation.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Settings.UI.Library.Helpers
+{
+    public class SearchLocation
+    {
+        public string City { get; set; }
+
+        public string Country { get; set; }
+
+        public double Latitude { get; set; }
+
+        public double Longitude { get; set; }
+
+        public SearchLocation(string city, string country, double latitude, double longitude)
+        {
+            City = city;
+            Country = country;
+            Latitude = latitude;
+            Longitude = longitude;
+        }
+    }
+}

src/settings-ui/Settings.UI.Library/Helpers/SearchLocationLoader.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Text;
+using Settings.UI.Library.Helpers;
+
+namespace Microsoft.PowerToys.Settings.UI.Helpers
+{
+    public static class SearchLocationLoader
+    {
+        private static readonly List<SearchLocation> LocationDataList = new List<SearchLocation>();
+
+        public static IEnumerable<SearchLocation> GetAll()
+        {
+            return LocationDataList
+                .GroupBy(l => $"{l.Country}|{l.City}|{l.Latitude.ToString(CultureInfo.InvariantCulture)}|{l.Longitude.ToString(CultureInfo.InvariantCulture)}")
+                .Select(g => g.First())
+                .OrderBy(l => l.Country, StringComparer.OrdinalIgnoreCase)
+                .ThenBy(l => l.City, StringComparer.OrdinalIgnoreCase);
+        }
+    }
+}

src/settings-ui/Settings.UI.Library/Helpers/SunCalc.cs

@@ -0,0 +1,131 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace Microsoft.PowerToys.Settings.UI.Library.Helpers
+{
+    public static class SunCalc
+    {
+        public static SunTimes CalculateSunriseSunset(double latitude, double longitude, int year, int month, int day)
+        {
+            double zenith = 90.833; // official sunrise/sunset
+
+            int n1 = (int)Math.Floor(275.0 * month / 9.0);
+            int n2 = (int)Math.Floor((month + 9.0) / 12.0);
+            int n3 = (int)Math.Floor(1.0 + Math.Floor((year - (4.0 * Math.Floor(year / 4.0)) + 2.0) / 3.0));
+            int n = n1 - (n2 * n3) + day - 30;
+
+            double? riseUT = CalcTime(isSunrise: true);
+            double? setUT = CalcTime(isSunrise: false);
+
+            var riseLocal = ToLocal(riseUT, year, month, day);
+            var setLocal = ToLocal(setUT, year, month, day);
+
+            var result = new SunTimes
+            {
+                HasSunrise = riseLocal.HasValue,
+                HasSunset = setLocal.HasValue,
+                SunriseHour = riseLocal?.Hour ?? -1,
+                SunriseMinute = riseLocal?.Minute ?? -1,
+                SunsetHour = setLocal?.Hour ?? -1,
+                SunsetMinute = setLocal?.Minute ?? -1,
+            };
+
+            return result;
+
+            // Local functions
+            double? CalcTime(bool isSunrise)
+            {
+                double lngHour = longitude / 15.0;
+                double t = isSunrise ? n + ((6 - lngHour) / 24.0) : n + ((18 - lngHour) / 24.0);
+
+                double m1 = (0.9856 * t) - 3.289;
+                double l = m1 + (1.916 * Math.Sin(Deg2Rad(m1))) + (0.020 * Math.Sin(2 * Deg2Rad(m1))) + 282.634;
+                l = NormalizeDegrees(l);
+
+                double rA = Rad2Deg(Math.Atan(0.91764 * Math.Tan(Deg2Rad(l))));
+                rA = NormalizeDegrees(rA);
+
+                double lquadrant = Math.Floor(l / 90.0) * 90.0;
+                double rAquadrant = Math.Floor(rA / 90.0) * 90.0;
+                rA = rA + (lquadrant - rAquadrant);
+                rA /= 15.0;
+
+                double sinDec = 0.39782 * Math.Sin(Deg2Rad(l));
+                double cosDec = Math.Cos(Math.Asin(sinDec));
+
+                double cosH = (Math.Cos(Deg2Rad(zenith)) - (sinDec * Math.Sin(Deg2Rad(latitude))))
+                            / (cosDec * Math.Cos(Deg2Rad(latitude)));
+
+                if (cosH > 1.0 || cosH < -1.0)
+                {
+                    // Sun never rises or never sets on this date at this location
+                    return null;
+                }
+
+                double h = isSunrise ? 360.0 - Rad2Deg(Math.Acos(cosH)) : Rad2Deg(Math.Acos(cosH));
+                h /= 15.0;
+
+                double t1 = h + rA - (0.06571 * t) - 6.622;
+                double uT = t1 - lngHour;
+                uT = NormalizeHours(uT);
+
+                return uT;
+            }
+
+            static (int Hour, int Minute)? ToLocal(double? ut, int y, int m, int d)
+            {
+                if (!ut.HasValue)
+                {
+                    return null;
+                }
+
+                // Convert fractional hours to hh:mm with proper rounding
+                int hours = (int)Math.Floor(ut.Value);
+                int minutes = (int)((ut.Value - hours) * 60.0);
+
+                // Normalize minute overflow
+                if (minutes == 60)
+                {
+                    minutes = 0;
+                    hours = (hours + 1) % 24;
+                }
+
+                // Build a UTC DateTime on the given date
+                var utc = new DateTime(y, m, d, hours, minutes, 0, DateTimeKind.Utc);
+
+                // Convert to local time using system time zone rules for that date
+                var local = TimeZoneInfo.ConvertTimeFromUtc(utc, TimeZoneInfo.Local);
+
+                return (local.Hour, local.Minute);
+            }
+
+            static double Deg2Rad(double deg) => deg * Math.PI / 180.0;
+            static double Rad2Deg(double rad) => rad * 180.0 / Math.PI;
+
+            static double NormalizeDegrees(double angle)
+            {
+                angle %= 360.0;
+                if (angle < 0)
+                {
+                    angle += 360.0;
+                }
+
+                return angle;
+            }
+
+            static double NormalizeHours(double hours)
+            {
+                hours %= 24.0;
+                if (hours < 0)
+                {
+                    hours += 24.0;
+                }
+
+                return hours;
+            }
+        }
+    }
+}

src/settings-ui/Settings.UI.Library/Helpers/SunTimes.cs

@@ -0,0 +1,24 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.PowerToys.Settings.UI.Library.Helpers
+{
+    public struct SunTimes
+    {
+        public int SunriseHour;
+        public int SunriseMinute;
+        public int SunsetHour;
+        public int SunsetMinute;
+        public string Text;
+
+        public bool HasSunrise;
+        public bool HasSunset;
+    }
+}

src/settings-ui/Settings.UI.Library/LightSwitchProperties.cs

@@ -0,0 +1,66 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text.Json.Serialization;
+
+namespace Microsoft.PowerToys.Settings.UI.Library
+{
+    public class LightSwitchProperties
+    {
+        public const bool DefaultChangeSystem = true;
+        public const bool DefaultChangeApps = true;
+        public const int DefaultLightTime = 480;
+        public const int DefaultDarkTime = 1200;
+        public const int DefaultSunriseOffset = 0;
+        public const int DefaultSunsetOffset = 0;
+        public const string DefaultLatitude = "0.0";
+        public const string DefaultLongitude = "0.0";
+        public const string DefaultScheduleMode = "FixedHours";
+        public static readonly HotkeySettings DefaultToggleThemeHotkey = new HotkeySettings(true, true, false, true, 0x44); // Ctrl+Win+Shift+D
+
+        public LightSwitchProperties()
+        {
+            ChangeSystem = new BoolProperty(DefaultChangeSystem);
+            ChangeApps = new BoolProperty(DefaultChangeApps);
+            LightTime = new IntProperty(DefaultLightTime);
+            DarkTime = new IntProperty(DefaultDarkTime);
+            Latitude = new StringProperty(DefaultLatitude);
+            Longitude = new StringProperty(DefaultLongitude);
+            SunriseOffset = new IntProperty(DefaultSunriseOffset);
+            SunsetOffset = new IntProperty(DefaultSunsetOffset);
+            ScheduleMode = new StringProperty(DefaultScheduleMode);
+            ToggleThemeHotkey = new KeyboardKeysProperty(DefaultToggleThemeHotkey);
+        }
+
+        [JsonPropertyName("changeSystem")]
+        public BoolProperty ChangeSystem { get; set; }
+
+        [JsonPropertyName("changeApps")]
+        public BoolProperty ChangeApps { get; set; }
+
+        [JsonPropertyName("lightTime")]
+        public IntProperty LightTime { get; set; }
+
+        [JsonPropertyName("darkTime")]
+        public IntProperty DarkTime { get; set; }
+
+        [JsonPropertyName("sunrise_offset")]
+        public IntProperty SunriseOffset { get; set; }
+
+        [JsonPropertyName("sunset_offset")]
+        public IntProperty SunsetOffset { get; set; }
+
+        [JsonPropertyName("latitude")]
+        public StringProperty Latitude { get; set; }
+
+        [JsonPropertyName("longitude")]
+        public StringProperty Longitude { get; set; }
+
+        [JsonPropertyName("scheduleMode")]
+        public StringProperty ScheduleMode { get; set; }
+
+        [JsonPropertyName("toggle-theme-hotkey")]
+        public KeyboardKeysProperty ToggleThemeHotkey { get; set; }
+    }
+}

src/settings-ui/Settings.UI.Library/LightSwitchSettings.cs

@@ -0,0 +1,58 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Reflection;
+using System.Text.Json.Serialization;
+using Microsoft.PowerToys.Settings.UI.Library;
+using Microsoft.PowerToys.Settings.UI.Library.Interfaces;
+
+namespace Settings.UI.Library
+{
+    public class LightSwitchSettings : BasePTModuleSettings, ISettingsConfig, ICloneable
+    {
+        public const string ModuleName = "LightSwitch";
+
+        public LightSwitchSettings()
+        {
+            Name = ModuleName;
+            Version = Assembly.GetExecutingAssembly().GetName().Version.ToString();
+            Properties = new LightSwitchProperties();
+        }
+
+        [JsonPropertyName("properties")]
+        public LightSwitchProperties Properties { get; set; }
+
+        public object Clone()
+        {
+            return new LightSwitchSettings()
+            {
+                Name = Name,
+                Version = Version,
+                Properties = new LightSwitchProperties()
+                {
+                    ChangeSystem = new BoolProperty(Properties.ChangeSystem.Value),
+                    ChangeApps = new BoolProperty(Properties.ChangeApps.Value),
+                    ScheduleMode = new StringProperty(Properties.ScheduleMode.Value),
+                    LightTime = new IntProperty((int)Properties.LightTime.Value),
+                    DarkTime = new IntProperty((int)Properties.DarkTime.Value),
+                    SunriseOffset = new IntProperty((int)Properties.SunriseOffset.Value),
+                    SunsetOffset = new IntProperty((int)Properties.SunsetOffset.Value),
+                    Latitude = new StringProperty(Properties.Latitude.Value),
+                    Longitude = new StringProperty(Properties.Longitude.Value),
+                },
+            };
+        }
+
+        public string GetModuleName()
+        {
+            return Name;
+        }
+
+        public bool UpgradeSettingsConfiguration()
+        {
+            return false;
+        }
+    }
+}

src/settings-ui/Settings.UI.Library/SndLightSwitchSettings.cs

@@ -0,0 +1,30 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Settings.UI.Library;
+
+namespace Microsoft.PowerToys.Settings.UI.Library
+{
+    public class SndLightSwitchSettings
+    {
+        [JsonPropertyName("LightSwitch")]
+        public LightSwitchSettings Settings { get; set; }
+
+        public SndLightSwitchSettings()
+        {
+        }
+
+        public SndLightSwitchSettings(LightSwitchSettings settings)
+        {
+            Settings = settings;
+        }
+
+        public string ToJsonString()
+        {
+            return JsonSerializer.Serialize(this);
+        }
+    }
+}

src/settings-ui/Settings.UI/Converters/EnumToVisibilityConverter.cs

@@ -0,0 +1,37 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Data;
+
+namespace Microsoft.PowerToys.Settings.UI.Converters
+{
+    public partial class EnumToVisibilityConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, string language)
+        {
+            if (value == null || parameter == null)
+            {
+                return Visibility.Collapsed;
+            }
+
+            string enumString = value.ToString();
+            string targetString = parameter.ToString();
+
+            return enumString.Equals(targetString, StringComparison.OrdinalIgnoreCase)
+                ? Visibility.Visible
+                : Visibility.Collapsed;
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, string language)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

src/settings-ui/Settings.UI/Converters/TimeSpanToFriendlyTimeConverter.cs

@@ -0,0 +1,25 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Microsoft.PowerToys.Settings.UI.Helpers;
+using Microsoft.PowerToys.Settings.UI.Library;
+using Microsoft.UI.Xaml.Data;
+
+namespace Microsoft.PowerToys.Settings.UI.Converters;
+
+public sealed partial class TimeSpanToFriendlyTimeConverter : IValueConverter
+{
+    public object Convert(object value, Type targetType, object parameter, string language)
+    {
+        if (value is TimeSpan time)
+        {
+            return TimeSpanHelper.Convert(time);
+        }
+
+        return string.Empty;
+    }
+
+    public object ConvertBack(object value, Type targetType, object parameter, string language) => new NotImplementedException();
+}

src/settings-ui/Settings.UI/Helpers/ModuleHelper.cs

@@ -52,6 +52,7 @@ namespace Microsoft.PowerToys.Settings.UI.Helpers
                 case ModuleType.CmdPal: return generalSettingsConfig.Enabled.CmdPal;
                 case ModuleType.ColorPicker: return generalSettingsConfig.Enabled.ColorPicker;
                 case ModuleType.CropAndLock: return generalSettingsConfig.Enabled.CropAndLock;
+                case ModuleType.LightSwitch: return generalSettingsConfig.Enabled.LightSwitch;
                 case ModuleType.EnvironmentVariables: return generalSettingsConfig.Enabled.EnvironmentVariables;
                 case ModuleType.FancyZones: return generalSettingsConfig.Enabled.FancyZones;
                 case ModuleType.FileLocksmith: return generalSettingsConfig.Enabled.FileLocksmith;
@@ -88,6 +89,7 @@ namespace Microsoft.PowerToys.Settings.UI.Helpers
                 case ModuleType.CmdPal: generalSettingsConfig.Enabled.CmdPal = isEnabled; break;
                 case ModuleType.ColorPicker: generalSettingsConfig.Enabled.ColorPicker = isEnabled; break;
                 case ModuleType.CropAndLock: generalSettingsConfig.Enabled.CropAndLock = isEnabled; break;
+                case ModuleType.LightSwitch: generalSettingsConfig.Enabled.LightSwitch = isEnabled; break;
                 case ModuleType.EnvironmentVariables: generalSettingsConfig.Enabled.EnvironmentVariables = isEnabled; break;
                 case ModuleType.FancyZones: generalSettingsConfig.Enabled.FancyZones = isEnabled; break;
                 case ModuleType.FileLocksmith: generalSettingsConfig.Enabled.FileLocksmith = isEnabled; break;
@@ -159,6 +161,7 @@ namespace Microsoft.PowerToys.Settings.UI.Helpers
                 ModuleType.CmdPal => typeof(CmdPalPage),
                 ModuleType.ColorPicker => typeof(ColorPickerPage),
                 ModuleType.CropAndLock => typeof(CropAndLockPage),
+                ModuleType.LightSwitch => typeof(LightSwitchPage),
                 ModuleType.EnvironmentVariables => typeof(EnvironmentVariablesPage),
                 ModuleType.FancyZones => typeof(FancyZonesPage),
                 ModuleType.FileLocksmith => typeof(FileLocksmithPage),

src/settings-ui/Settings.UI/Helpers/TimeSpanHelper.cs

@@ -0,0 +1,38 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+
+namespace Microsoft.PowerToys.Settings.UI.Helpers;
+
+public static class TimeSpanHelper
+{
+    public static string Convert(TimeSpan? time)
+    {
+        if (time is not TimeSpan ts)
+        {
+            return string.Empty;
+        }
+
+        // If user passed in a negative TimeSpan, normalize
+        if (ts < TimeSpan.Zero)
+        {
+            ts = ts.Duration();
+        }
+
+        // Map the TimeSpan to a DateTime on today's date
+        var dt = DateTime.Today.Add(ts);
+
+        // This pattern automatically respects system 12/24-hour setting
+        string pattern = CultureInfo.CurrentCulture.DateTimeFormat.ShortTimePattern;
+
+        return dt.ToString(pattern, CultureInfo.CurrentCulture);
+    }
+}

src/settings-ui/Settings.UI/OOBE/Enums/PowerToysModules.cs

@@ -20,6 +20,7 @@ namespace Microsoft.PowerToys.Settings.UI.OOBE.Enums
         FileExplorer,
         ImageResizer,
         KBM,
+        LightSwitch,
         MouseUtils,
         MouseWithoutBorders,
         Peek,

src/settings-ui/Settings.UI/PowerToys.Settings.csproj

@@ -22,6 +22,7 @@
 	<ItemGroup>
 		<None Remove="Assets\Settings\Modules\APDialog.dark.png" />
 		<None Remove="Assets\Settings\Modules\APDialog.light.png" />
+		<None Remove="Assets\Settings\Modules\LightSwitch.png" />
 		<None Remove="SettingsXAML\Controls\Dashboard\CheckUpdateControl.xaml" />
 		<None Remove="SettingsXAML\Controls\Dashboard\ShortcutConflictControl.xaml" />
 		<None Remove="SettingsXAML\Controls\KeyVisual\KeyCharPresenter.xaml" />
@@ -156,7 +157,9 @@
 		</None>
 		<None Update="Assets\Settings\Scripts\DisableModule.ps1">
 			<CopyToOutputDirectory>Always</CopyToOutputDirectory>
-		</None>		<Page Update="SettingsXAML\Controls\TitleBar\TitleBar.xaml">
+		</None>
+		<Page Update="SettingsXAML\Controls\TitleBar\TitleBar.xaml">
+			<Generator>MSBuild:Compile</Generator>
 		</Page>
 		<Page Update="SettingsXAML\Controls\KeyVisual\KeyCharPresenter.xaml">
 			<Generator>MSBuild:Compile</Generator>
@@ -170,6 +173,12 @@
 		<Page Update="SettingsXAML\Controls\Dashboard\CheckUpdateControl.xaml">
 			<Generator>MSBuild:Compile</Generator>
 		</Page>
+		    <Page Update="SettingsXAML\Controls\Timeline\TimelineStyles.xaml">
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
+    <Page Update="SettingsXAML\Controls\Timeline\Timeline.xaml">
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
 	</ItemGroup>
 
 	<ItemGroup>

src/settings-ui/Settings.UI/SerializationContext/SourceGenerationContextContext.cs

@@ -10,6 +10,7 @@ using System.Text.Json.Serialization;
 using System.Threading.Tasks;
 using Microsoft.PowerToys.Settings.UI.Helpers;
 using Microsoft.PowerToys.Settings.UI.Library;
+using Settings.UI.Library;
 
 namespace Microsoft.PowerToys.Settings.UI.SerializationContext;
 
@@ -22,6 +23,7 @@ namespace Microsoft.PowerToys.Settings.UI.SerializationContext;
 [JsonSerializable(typeof(FileLocksmithSettings))]
 [JsonSerializable(typeof(FindMyMouseSettings))]
 [JsonSerializable(typeof(IList<PowerToysReleaseInfo>))]
+[JsonSerializable(typeof(LightSwitchSettings))]
 [JsonSerializable(typeof(MeasureToolSettings))]
 [JsonSerializable(typeof(MouseHighlighterSettings))]
 [JsonSerializable(typeof(MouseJumpSettings))]

src/settings-ui/Settings.UI/SettingsXAML/App.xaml

@@ -17,6 +17,7 @@
                 <ResourceDictionary Source="/SettingsXAML/Styles/InfoBadge.xaml" />
                 <ResourceDictionary Source="/SettingsXAML/Themes/Colors.xaml" />
                 <ResourceDictionary Source="/SettingsXAML/Themes/Generic.xaml" />
+                <ResourceDictionary Source="/SettingsXAML/Controls/Timeline/TimelineStyles.xaml" />
 
                 <!--  Other merged dictionaries here  -->
             </ResourceDictionary.MergedDictionaries>

src/settings-ui/Settings.UI/SettingsXAML/App.xaml.cs

@@ -417,6 +417,7 @@ namespace Microsoft.PowerToys.Settings.UI
                 case "Awake": return typeof(AwakePage);
                 case "CmdNotFound": return typeof(CmdNotFoundPage);
                 case "ColorPicker": return typeof(ColorPickerPage);
+                case "LightSwitch": return typeof(LightSwitchPage);
                 case "FancyZones": return typeof(FancyZonesPage);
                 case "FileLocksmith": return typeof(FileLocksmithPage);
                 case "Run": return typeof(PowerLauncherPage);

src/settings-ui/Settings.UI/SettingsXAML/Controls/SettingsPageControl/SettingsPageControl.xaml

@@ -28,7 +28,7 @@
             Style="{StaticResource TitleTextBlockStyle}"
             Text="{x:Bind ModuleTitle}" />
 
-        <ScrollViewer Grid.Row="1">
+        <ScrollViewer Grid.Row="1" AutomationProperties.AutomationId="PageScrollViewer">
             <Grid
                 Padding="0,0,20,48"
                 ChildrenTransitions="{StaticResource SettingsCardsAnimations}"

src/settings-ui/Settings.UI/SettingsXAML/Controls/Timeline/Timeline.xaml

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<UserControl
+    x:Class="Microsoft.PowerToys.Settings.UI.Controls.Timeline"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:local="using:Microsoft.PowerToys.Settings.UI.Controls"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d">
+
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="Auto" />
+        </Grid.RowDefinitions>
+
+        <Canvas
+            x:Name="HeaderCanvas"
+            Grid.Row="0"
+            Height="24" />
+
+        <!--  Timeline (bands + ticks + labels)  -->
+        <Border
+            Grid.Row="1"
+            BorderBrush="{ThemeResource CardStrokeColorDefaultBrush}"
+            BorderThickness="1"
+            CornerRadius="{ThemeResource OverlayCornerRadius}">
+            <Canvas
+                x:Name="TimelineCanvas"
+                Height="36"
+                Loaded="TimelineCanvas_Loaded" />
+        </Border>
+
+        <!--  Below-chart annotations (sunrise/sunset panels + major labels)  -->
+        <Canvas
+            x:Name="AnnotationCanvas"
+            Grid.Row="2"
+            Height="32" />
+    </Grid>
+</UserControl>

src/settings-ui/Settings.UI/SettingsXAML/Controls/Timeline/Timeline.xaml.cs

@@ -0,0 +1,664 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using Microsoft.PowerToys.Settings.UI.Helpers;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Automation;
+using Microsoft.UI.Xaml.Automation.Peers;
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Shapes;
+using Windows.Foundation;
+
+namespace Microsoft.PowerToys.Settings.UI.Controls
+{
+    public sealed partial class Timeline : UserControl
+    {
+        public TimeSpan StartTime
+        {
+            get => (TimeSpan)GetValue(StartTimeProperty);
+            set => SetValue(StartTimeProperty, value);
+        }
+
+        public static readonly DependencyProperty StartTimeProperty = DependencyProperty.Register(nameof(StartTime), typeof(TimeSpan), typeof(Timeline), new PropertyMetadata(defaultValue: new TimeSpan(22, 0, 0), OnTimeChanged));
+
+        public TimeSpan EndTime
+        {
+            get => (TimeSpan)GetValue(EndTimeProperty);
+            set => SetValue(EndTimeProperty, value);
+        }
+
+        public static readonly DependencyProperty EndTimeProperty = DependencyProperty.Register(nameof(EndTime), typeof(TimeSpan), typeof(Timeline), new PropertyMetadata(defaultValue: new TimeSpan(7, 0, 0), OnTimeChanged));
+
+        public TimeSpan? Sunrise
+        {
+            get => (TimeSpan?)GetValue(SunriseProperty);
+            set => SetValue(SunriseProperty, value);
+        }
+
+        public static readonly DependencyProperty SunriseProperty = DependencyProperty.Register(nameof(Sunrise), typeof(TimeSpan), typeof(Timeline), new PropertyMetadata(defaultValue: null, OnTimeChanged));
+
+        public TimeSpan? Sunset
+        {
+            get => (TimeSpan?)GetValue(SunsetProperty);
+            set => SetValue(SunsetProperty, value);
+        }
+
+        public static readonly DependencyProperty SunsetProperty = DependencyProperty.Register(nameof(Sunset), typeof(TimeSpan), typeof(Timeline), new PropertyMetadata(defaultValue: null, OnTimeChanged));
+
+        private readonly List<int> _tickHours = new();
+
+        // Locale 24h/12h
+        private readonly bool _is24h = CultureInfo.CurrentCulture.DateTimeFormat.ShortTimePattern.Contains('H');
+
+        // Visuals
+        private readonly List<Line> _ticks = new();
+        private readonly List<TextBlock> _majorTickBottomLabels = new(); // 00,06,12,18,24 (below)
+
+        private readonly List<Border> _darkRects = new(); // up to 2 (wrap)
+        private readonly List<Border> _lightRects = new(); // up to 2 (complement)
+
+        private TextBlock _startEdgeLabel; // top-of-chart
+        private TextBlock _endEdgeLabel;
+
+        private Line _sunriseTick;
+        private Line _sunsetTick;
+
+        // Add/replace these constants (top of your class)
+        private const int TickHourStep = 2; // <-- every 2 hours
+
+        private StackPanel _sunrisePanel;  // icon + time (below chart)
+        private StackPanel _sunsetPanel;
+
+        public Timeline()
+        {
+            this.InitializeComponent();
+            this.Loaded += Timeline_Loaded;
+            this.IsEnabledChanged += Timeline_IsEnabledChanged;
+        }
+
+        protected override AutomationPeer OnCreateAutomationPeer()
+        {
+            return new TimelineAutomationPeer(this);
+        }
+
+        private void Timeline_Loaded(object sender, RoutedEventArgs e)
+        {
+            CheckEnabledState();
+        }
+
+        private void Timeline_IsEnabledChanged(object sender, DependencyPropertyChangedEventArgs e)
+        {
+            CheckEnabledState();
+        }
+
+        private void CheckEnabledState()
+        {
+            if (IsEnabled)
+            {
+                this.Opacity = 1.0;
+            }
+            else
+            {
+                this.Opacity = 0.4;
+            }
+        }
+
+        private static void OnTimeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            ((Timeline)d).Setup();
+        }
+
+        private void Setup()
+        {
+            EnsureBands();
+            EnsureTicks();
+            EnsureStartEndEdgeLabels();
+            EnsureSunriseSunsetTicks();
+            EnsureSunPanels();
+            EnsureMajorTickLabels();
+            UpdateAll();
+        }
+
+        private void TimelineCanvas_Loaded(object sender, RoutedEventArgs e)
+        {
+            // SizeChanged wiring here (as requested)
+            HeaderCanvas.SizeChanged += (_, __) => UpdateAll();
+            TimelineCanvas.SizeChanged += (_, __) => UpdateAll();
+            AnnotationCanvas.SizeChanged += (_, __) => UpdateAll();
+            Setup();
+        }
+
+        private void UpdateAll()
+        {
+            UpdateBandsLayout();
+            UpdateTicksLayout();
+            UpdateStartEndEdgeLabelsLayout();
+            UpdateSunriseSunsetTicksLayout();
+            UpdateSunPanelsLayout();
+            UpdateMajorTickLabelsLayout();
+            AutomationProperties.SetHelpText(
+                this,
+                $"Start={StartTime};End={EndTime};Sunrise={Sunrise};Sunset={Sunset}");
+        }
+
+        // ===== Ticks =====
+        private void EnsureTicks()
+        {
+            if (_ticks.Count > 0)
+            {
+                return;
+            }
+
+            _tickHours.Clear();
+
+            // Build ticks at 0,2,4,...,24 but skip the first/last MAJOR ticks (0 and 24)
+            for (int hour = 0; hour <= 24; hour += TickHourStep)
+            {
+                bool isMajor = hour % 6 == 0;
+                if (isMajor && (hour == 0 || hour == 24))
+                {
+                    continue; // skip first/last major ticks
+                }
+
+                var line = new Line
+                {
+                    Style = (Style)Application.Current.Resources[isMajor ? "MajorHourTickStyle" : "HourTickStyle"],
+                };
+
+                Canvas.SetZIndex(line, 0); // above bands (adjust if needed)
+
+                _ticks.Add(line);
+                _tickHours.Add(hour);
+
+                // If you actually want these IN the chart, use TimelineCanvas instead:
+                AnnotationCanvas.Children.Add(line); // or TimelineCanvas.Children.Add(line);
+            }
+        }
+
+        private void UpdateTicksLayout()
+        {
+            double w = TimelineCanvas.ActualWidth;
+            double h = TimelineCanvas.ActualHeight; // keeping your offset
+            if (w <= 0 || h <= 0)
+            {
+                return;
+            }
+
+            double minorLen = h * 0.1;
+            double majorLen = h * 0.2;
+
+            for (int i = 0; i < _ticks.Count; i++)
+            {
+                int hour = _tickHours[i];
+                double x = Math.Round((hour / 24.0) * w);
+
+                var line = _ticks[i];
+                double len = (hour % 6 == 0) ? majorLen : minorLen;
+
+                line.X1 = x;
+                line.Y1 = 0;
+                line.X2 = x;
+                line.Y2 = len;
+            }
+        }
+
+        // ===== Bands (Dark + Light) =====
+        private void EnsureBands()
+        {
+            if (_darkRects.Count == 0)
+            {
+                _darkRects.Add(MakeBandRect(isDark: false));
+                _darkRects.Add(MakeBandRect(isDark: false));
+            }
+
+            if (_lightRects.Count == 0)
+            {
+                _lightRects.Add(MakeBandRect(isDark: true));
+                _lightRects.Add(MakeBandRect(isDark: true));
+            }
+        }
+
+        private Border MakeBandRect(bool isDark)
+        {
+            var r = new Border();
+            if (isDark)
+            {
+                r.Style = (Style)Application.Current.Resources["DarkBandStyle"];
+                FontIcon icon = new FontIcon();
+                icon.Style = (Style)Application.Current.Resources["DarkBandIconStyle"];
+                r.Child = icon;
+            }
+            else
+            {
+                r.Style = (Style)Application.Current.Resources["LightBandStyle"];
+            }
+
+            Canvas.SetZIndex(r, 5); // below ticks/labels
+            TimelineCanvas.Children.Add(r);
+            return r;
+        }
+
+        private void UpdateBandsLayout()
+        {
+            double w = TimelineCanvas.ActualWidth;
+            double h = TimelineCanvas.ActualHeight;
+            if (w <= 0 || h <= 0)
+            {
+                return;
+            }
+
+            foreach (var r in _darkRects)
+            {
+                r.Height = h;
+                Canvas.SetTop(r, 0);
+            }
+
+            foreach (var r in _lightRects)
+            {
+                r.Height = h;
+                Canvas.SetTop(r, 0);
+            }
+
+            var darkRanges = ToRanges(StartTime, EndTime);       // 1 or 2 segments
+            var lightRanges = ComplementRanges(darkRanges);       // 0..2
+
+            LayoutRangeRects(_darkRects, darkRanges, w);
+            LayoutRangeRects(_lightRects, lightRanges, w);
+        }
+
+        private static void LayoutRangeRects(List<Border> rects, List<(TimeSpan Start, TimeSpan End)> ranges, double width)
+        {
+            for (int i = 0; i < rects.Count; i++)
+            {
+                if (i < ranges.Count)
+                {
+                    var (start, end) = ranges[i];
+                    double x = Math.Round((start.TotalHours / 24.0) * width);
+                    double x2 = Math.Round((end.TotalHours / 24.0) * width);
+
+                    var r = rects[i];
+                    Canvas.SetLeft(r, x);
+                    r.Width = Math.Max(0, x2 - x);
+                    r.Visibility = Visibility.Visible;
+                }
+                else
+                {
+                    rects[i].Visibility = Visibility.Collapsed;
+                }
+            }
+        }
+
+        private static List<(TimeSpan Start, TimeSpan End)> ToRanges(TimeSpan start, TimeSpan end)
+        {
+            // Full day
+            if (start == end)
+            {
+                return new() { (TimeSpan.Zero, TimeSpan.FromHours(24)) };
+            }
+
+            if (start < end)
+            {
+                return new() { (start, end) };
+            }
+
+            // Wraps midnight
+            return new()
+        {
+            (start, TimeSpan.FromHours(24)),
+            (TimeSpan.Zero, end),
+        };
+        }
+
+        private static List<(TimeSpan Start, TimeSpan End)> ComplementRanges(List<(TimeSpan Start, TimeSpan End)> dark)
+        {
+            var res = new List<(TimeSpan, TimeSpan)>();
+
+            // If dark covers the full day, there is no light
+            if (dark.Count == 1 && dark[0].Start == TimeSpan.Zero && dark[0].End == TimeSpan.FromHours(24))
+            {
+                return res;
+            }
+
+            if (dark.Count == 1)
+            {
+                var (ds, de) = dark[0];
+                if (ds > TimeSpan.Zero)
+                {
+                    res.Add((TimeSpan.Zero, ds));
+                }
+
+                if (de < TimeSpan.FromHours(24))
+                {
+                    res.Add((de, TimeSpan.FromHours(24)));
+                }
+            }
+            else
+            {
+                // dark[0] = [a,24), dark[1] = [0,b) => single light [b,a)
+                var a = dark[0].Start;
+                var b = dark[1].End;
+                res.Add((b, a));
+            }
+
+            return res;
+        }
+
+        // ===== Start & End labels (TOP of chart, ABOVE rectangles) =====
+        private void EnsureStartEndEdgeLabels()
+        {
+            if (_startEdgeLabel == null)
+            {
+                _startEdgeLabel = new TextBlock { Style = (Style)Application.Current.Resources["EdgeLabelStyle"] };
+                HeaderCanvas.Children.Add(_startEdgeLabel);
+                Canvas.SetZIndex(_startEdgeLabel, 25);
+            }
+
+            if (_endEdgeLabel == null)
+            {
+                _endEdgeLabel = new TextBlock { Style = (Style)Application.Current.Resources["EdgeLabelStyle"] };
+                HeaderCanvas.Children.Add(_endEdgeLabel);
+                Canvas.SetZIndex(_endEdgeLabel, 25);
+            }
+        }
+
+        private void UpdateStartEndEdgeLabelsLayout()
+        {
+            double w = TimelineCanvas.ActualWidth;
+            if (w <= 0)
+            {
+                return;
+            }
+
+            _startEdgeLabel.Text = TimeSpanHelper.Convert(StartTime);
+            _endEdgeLabel.Text = TimeSpanHelper.Convert(EndTime);
+
+            PlaceTopLabelAtTime(_startEdgeLabel, StartTime, w);
+            PlaceTopLabelAtTime(_endEdgeLabel, EndTime, w);
+        }
+
+        private void PlaceTopLabelAtTime(TextBlock tb, TimeSpan t, double timelineWidth)
+        {
+            double x = Math.Round((t.TotalHours / 24.0) * timelineWidth);
+            double textW = MeasureTextWidth(tb);
+            double desiredLeft = x - (textW / 2.0);
+
+            Canvas.SetLeft(tb, Clamp(desiredLeft, 0, timelineWidth - textW));
+            Canvas.SetTop(tb, 0);
+            tb.Visibility = Visibility.Visible;
+        }
+
+        // ===== Sunrise/Sunset ticks on chart =====
+        private void EnsureSunriseSunsetTicks()
+        {
+            if (_sunriseTick == null)
+            {
+                _sunriseTick = new Line { Style = (Style)Application.Current.Resources["SunRiseMarkerTickStyle"] };
+                TimelineCanvas.Children.Add(_sunriseTick);
+                Canvas.SetZIndex(_sunriseTick, 12);
+            }
+
+            if (_sunsetTick == null)
+            {
+                _sunsetTick = new Line { Style = (Style)Application.Current.Resources["SunSetMarkerTickStyle"] };
+                TimelineCanvas.Children.Add(_sunsetTick);
+                Canvas.SetZIndex(_sunsetTick, 12);
+            }
+        }
+
+        private void UpdateSunriseSunsetTicksLayout()
+        {
+            double w = TimelineCanvas.ActualWidth;
+            double h = TimelineCanvas.ActualHeight + 24;
+            if (w <= 0 || h <= 0)
+            {
+                return;
+            }
+
+            void Place(Line tick, TimeSpan t)
+            {
+                double x = Math.Round((t.TotalHours / 24.0) * w);
+                tick.X1 = x;
+                tick.X2 = x;
+                tick.Y1 = 0;
+                tick.Y2 = h;
+            }
+
+            if (_sunriseTick != null)
+            {
+                if (Sunrise.HasValue)
+                {
+                    Place(_sunriseTick, Sunrise.Value);
+                    _sunriseTick.Visibility = Visibility.Visible;
+                }
+                else
+                {
+                    _sunriseTick.Visibility = Visibility.Collapsed;
+                }
+            }
+
+            if (_sunsetTick != null)
+            {
+                if (Sunset.HasValue)
+                {
+                    Place(_sunsetTick, Sunset.Value);
+                    _sunsetTick.Visibility = Visibility.Visible;
+                }
+                else
+                {
+                    _sunsetTick.Visibility = Visibility.Collapsed;
+                }
+            }
+        }
+
+        // ===== Sunrise/Sunset panels (below chart) =====
+        private void EnsureSunPanels()
+        {
+            if (_sunrisePanel == null)
+            {
+                _sunrisePanel = MakeSunPanel("\uEC8A");
+                AnnotationCanvas.Children.Add(_sunrisePanel);
+            }
+
+            if (_sunsetPanel == null)
+            {
+                _sunsetPanel = MakeSunPanel("\uED3A");
+                AnnotationCanvas.Children.Add(_sunsetPanel);
+            }
+        }
+
+        private StackPanel MakeSunPanel(string iconEmoji)
+        {
+            var icon = new FontIcon { Glyph = iconEmoji, Style = (Style)Application.Current.Resources["SunIconStyle"] };
+            var sp = new StackPanel { Orientation = Orientation.Vertical, Spacing = 2 };
+            sp.Children.Add(icon);
+            return sp;
+        }
+
+        private void UpdateSunPanelsLayout()
+        {
+            double timelineW = TimelineCanvas.ActualWidth;
+            double annotationW = AnnotationCanvas.ActualWidth;
+            if (annotationW <= 0)
+            {
+                annotationW = timelineW;
+            }
+
+            if (timelineW <= 0 || annotationW <= 0)
+            {
+                return;
+            }
+
+            void Place(StackPanel sp, TimeSpan t)
+            {
+                double panelW = MeasureElementWidth(sp);
+                double xTimeline = Math.Round((t.TotalHours / 24.0) * timelineW);
+                double left = Clamp(xTimeline - (panelW / 2.0), 0, annotationW - panelW);
+                Canvas.SetLeft(sp, left);
+                Canvas.SetTop(sp, 8);
+            }
+
+            if (_sunrisePanel != null)
+            {
+                if (Sunrise.HasValue)
+                {
+                    ToolTipService.SetToolTip(_sunrisePanel, $"Sunrise: {TimeSpanHelper.Convert(Sunrise.Value)}");
+                    _sunrisePanel.Visibility = Visibility.Visible;
+                    Place(_sunrisePanel, Sunrise.Value);
+                }
+                else
+                {
+                    ToolTipService.SetToolTip(_sunrisePanel, null);
+                    _sunrisePanel.Visibility = Visibility.Collapsed;
+                }
+            }
+
+            if (_sunsetPanel != null)
+            {
+                if (Sunset.HasValue)
+                {
+                    ToolTipService.SetToolTip(_sunsetPanel, $"Sunset: {TimeSpanHelper.Convert(Sunset.Value)}");
+                    _sunsetPanel.Visibility = Visibility.Visible;
+                    Place(_sunsetPanel, Sunset.Value);
+                }
+                else
+                {
+                    ToolTipService.SetToolTip(_sunsetPanel, null);
+                    _sunsetPanel.Visibility = Visibility.Collapsed;
+                }
+            }
+        }
+
+        // ===== Major labels BELOW chart (00,06,12,18,24) =====
+        private void EnsureMajorTickLabels()
+        {
+            if (_majorTickBottomLabels.Count > 0)
+            {
+                return;
+            }
+
+            // Includes 24:00 at end
+            for (int i = 0; i < 5; i++)
+            {
+                var tb = new TextBlock { Style = (Style)Application.Current.Resources["MajorTickLabelStyle"] };
+                Canvas.SetZIndex(tb, 5); // on annotation canvas
+                _majorTickBottomLabels.Add(tb);
+                AnnotationCanvas.Children.Add(tb);
+            }
+        }
+
+        private void UpdateMajorTickLabelsLayout()
+        {
+            double timelineW = TimelineCanvas.ActualWidth;
+            double annotationW = AnnotationCanvas.ActualWidth;
+            if (annotationW <= 0)
+            {
+                annotationW = timelineW;
+            }
+
+            if (timelineW <= 0 || annotationW <= 0)
+            {
+                return;
+            }
+
+            int[] hours = { 0, 6, 12, 18, 24 };
+
+            // 1) Place labels first
+            for (int i = 0; i < hours.Length; i++)
+            {
+                var tb = _majorTickBottomLabels[i];
+                var t = TimeSpan.FromHours(hours[i]);
+                tb.Text = TimeSpanHelper.Convert(t);
+
+                double xTimeline = Math.Round((t.TotalHours / 24.0) * timelineW);
+                double textW = MeasureTextWidth(tb);
+                double left = xTimeline - (textW / 2.0);
+
+                // Middle ones (06, 12) exact center; edges clamp inside canvas
+                if (i == 1 || i == 2)
+                {
+                    Canvas.SetLeft(tb, left);
+                }
+                else
+                {
+                    Canvas.SetLeft(tb, Clamp(left, 0, annotationW - textW));
+                }
+
+                Canvas.SetTop(tb, 8); // your existing baseline below chart
+                tb.Visibility = Visibility.Visible;
+            }
+
+            // 2) Compute sunrise/sunset occupied horizontal ranges (if present)
+            (double Left, double Right)? sunriseBounds = null;
+            (double Left, double Right)? sunsetBounds = null;
+
+            if (Sunrise.HasValue && _sunrisePanel != null)
+            {
+                sunriseBounds = GetAnnotationBoundsForTime(Sunrise.Value, timelineW, annotationW, _sunrisePanel);
+            }
+
+            if (Sunset.HasValue && _sunsetPanel != null)
+            {
+                sunsetBounds = GetAnnotationBoundsForTime(Sunset.Value, timelineW, annotationW, _sunsetPanel);
+            }
+
+            // 3) Hide any label that intersects the sunrise/sunset panel bounds
+            for (int i = 0; i < hours.Length; i++)
+            {
+                var tb = _majorTickBottomLabels[i];
+                if (tb.Visibility != Visibility.Visible)
+                {
+                    continue;
+                }
+
+                var lbl = GetLabelBounds(tb);
+
+                bool hide =
+                    (sunriseBounds.HasValue && Intersects(lbl, sunriseBounds.Value)) ||
+                    (sunsetBounds.HasValue && Intersects(lbl, sunsetBounds.Value)); // include sunset too; remove if you only want sunrise
+
+                tb.Visibility = hide ? Visibility.Collapsed : Visibility.Visible;
+            }
+        }
+
+        // ===== Utilities =====
+        private static double Clamp(double v, double min, double max) => Math.Max(min, Math.Min(max, v));
+
+        private static double MeasureElementWidth(FrameworkElement el)
+        {
+            el.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
+            return el.DesiredSize.Width;
+        }
+
+        private static double MeasureTextWidth(TextBlock tb)
+        {
+            tb.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
+            return tb.DesiredSize.Width;
+        }
+
+        private static bool Intersects((double Left, double Right) a, (double Left, double Right) b, double pad = 4)
+        {
+            // Horizontal overlap with padding
+            return !(a.Right + pad <= b.Left || b.Right + pad <= a.Left);
+        }
+
+        private (double Left, double Right) GetAnnotationBoundsForTime(TimeSpan t, double timelineW, double annotationW, FrameworkElement element)
+        {
+            // Compute the *actual* left/right the panel will occupy in AnnotationCanvas
+            double panelW = MeasureElementWidth(element);
+            double xTimeline = Math.Round((t.TotalHours / 24.0) * timelineW);
+            double left = Clamp(xTimeline - (panelW / 2.0), 0, annotationW - panelW);
+            return (left, left + panelW);
+        }
+
+        private (double Left, double Right) GetLabelBounds(TextBlock tb)
+        {
+            double w = MeasureTextWidth(tb);
+            double left = Canvas.GetLeft(tb);
+            return (left, left + w);
+        }
+    }
+}

src/settings-ui/Settings.UI/SettingsXAML/Controls/Timeline/TimelineAutomationPeer.cs

@@ -0,0 +1,39 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Automation;
+using Microsoft.UI.Xaml.Automation.Peers;
+
+namespace Microsoft.PowerToys.Settings.UI.Controls
+{
+    public partial class TimelineAutomationPeer : FrameworkElementAutomationPeer
+    {
+        public TimelineAutomationPeer(Timeline owner)
+            : base(owner)
+        {
+        }
+
+        protected override string GetClassNameCore() => "Timeline";
+
+        protected override AutomationControlType GetAutomationControlTypeCore()
+            => AutomationControlType.Custom;
+
+        protected override string GetAutomationIdCore()
+        {
+            var owner = (Timeline)Owner;
+            var id = AutomationProperties.GetAutomationId(owner);
+            return string.IsNullOrEmpty(id) ? base.GetAutomationIdCore() : id;
+        }
+
+        protected override string GetNameCore()
+        {
+            var owner = (Timeline)Owner;
+            var name = AutomationProperties.GetName(owner);
+            return !string.IsNullOrEmpty(name)
+                ? name
+                : $"Timeline from {owner.StartTime} to {owner.EndTime}";
+        }
+    }
+}

src/settings-ui/Settings.UI/SettingsXAML/Controls/Timeline/TimelineStyles.xaml

@@ -0,0 +1,84 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+
+    <Style x:Key="HourTickStyle" TargetType="Line">
+        <Setter Property="Stroke" Value="{ThemeResource TextFillColorTertiaryBrush}" />
+        <Setter Property="StrokeThickness" Value="1" />
+    </Style>
+
+    <Style
+        x:Key="MajorHourTickStyle"
+        BasedOn="{StaticResource HourTickStyle}"
+        TargetType="Line">
+        <Setter Property="StrokeThickness" Value="2" />
+        <Setter Property="Stroke" Value="{ThemeResource TextFillColorTertiaryBrush}" />
+    </Style>
+
+    <Style x:Key="SunRiseMarkerTickStyle" TargetType="Line">
+        <Setter Property="Stroke" Value="{ThemeResource TextFillColorTertiaryBrush}" />
+        <Setter Property="StrokeThickness" Value="1" />
+        <Setter Property="StrokeDashArray" Value="2,2" />
+    </Style>
+
+
+    <Style x:Key="SunSetMarkerTickStyle" TargetType="Line">
+        <Setter Property="Stroke" Value="{ThemeResource TextFillColorTertiaryBrush}" />
+        <Setter Property="StrokeThickness" Value="1" />
+        <Setter Property="StrokeDashArray" Value="2,2" />
+    </Style>
+
+    <!--  ===== Text / Labels =====  -->
+    <Style x:Key="EdgeLabelStyle" TargetType="TextBlock">
+        <Setter Property="FontSize" Value="14" />
+        <Setter Property="FontWeight" Value="SemiBold" />
+        <Setter Property="Foreground" Value="{ThemeResource AccentTextFillColorPrimaryBrush}" />
+        <Setter Property="IsHitTestVisible" Value="False" />
+    </Style>
+
+    <!--  Below-chart labels for 00/06/12/18/24  -->
+    <Style x:Key="MajorTickLabelStyle" TargetType="TextBlock">
+        <Setter Property="FontSize" Value="12" />
+        <Setter Property="Foreground" Value="{ThemeResource TextFillColorTertiaryBrush}" />
+        <Setter Property="IsHitTestVisible" Value="False" />
+    </Style>
+
+    <!--  Sunrise/Sunset panel styles  -->
+    <Style x:Key="SunIconStyle" TargetType="FontIcon">
+        <Setter Property="FontSize" Value="18" />
+        <Setter Property="Foreground" Value="{ThemeResource TextFillColorTertiaryBrush}" />
+        <Setter Property="HorizontalAlignment" Value="Center" />
+    </Style>
+
+    <!--  ===== Bands =====  -->
+    <Style x:Key="DarkBandStyle" TargetType="Border">
+        <!--<Setter Property="Background">
+            <Setter.Value>
+                <SolidColorBrush Opacity="0.6" Color="{ThemeResource SystemAccentColorDark1}"/>
+            </Setter.Value>
+        </Setter>-->
+        <Setter Property="Background" Value="{ThemeResource AccentFillColorTertiaryBrush}" />
+        <Setter Property="CornerRadius" Value="8" />
+        <Setter Property="Padding" Value="4" />
+        <Setter Property="ToolTipService.ToolTip" Value="Dark mode" />
+    </Style>
+
+    <Style x:Key="LightBandStyle" TargetType="Border">
+        <Setter Property="Background" Value="{ThemeResource CardBackgroundFillColorDefaultBrush}" />
+        <Setter Property="ToolTipService.ToolTip" Value="Light mode" />
+    </Style>
+
+    <Style x:Key="DarkBandIconStyle" TargetType="FontIcon">
+        <Setter Property="FontSize" Value="14" />
+        <Setter Property="Glyph" Value="&#xE793;" />
+        <Setter Property="Foreground" Value="{ThemeResource TextOnAccentFillColorPrimaryBrush}" />
+        <Setter Property="HorizontalAlignment" Value="Center" />
+    </Style>
+    <Style
+        x:Key="LightBandIconStyle"
+        BasedOn="{StaticResource DarkBandIconStyle}"
+        TargetType="FontIcon">
+        <Setter Property="Glyph" Value="&#xE706;" />
+        <Setter Property="Foreground" Value="{ThemeResource TextFillColorSecondaryBrush}" />
+    </Style>
+
+</ResourceDictionary>

src/settings-ui/Settings.UI/SettingsXAML/OOBE/Views/OobeLightSwitch.xaml

@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<Page
+    x:Class="Microsoft.PowerToys.Settings.UI.OOBE.Views.OobeLightSwitch"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:controls="using:Microsoft.PowerToys.Settings.UI.Controls"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:tkcontrols="using:CommunityToolkit.WinUI.Controls"
+    mc:Ignorable="d">
+
+    <controls:OOBEPageControl x:Uid="Oobe_LightSwitch" HeroImage="ms-appx:///Assets/Settings/Modules/OOBE/LightSwitch.png">
+        <controls:OOBEPageControl.PageContent>
+            <StackPanel Orientation="Vertical" Spacing="12">
+                <TextBlock x:Uid="Oobe_HowToUse" Style="{ThemeResource OobeSubtitleStyle}" />
+
+                <tkcontrols:MarkdownTextBlock x:Uid="Oobe_LightSwitch_HowToUse" />
+
+                <TextBlock x:Uid="Oobe_TipsAndTricks" Style="{ThemeResource OobeSubtitleStyle}" />
+
+                <tkcontrols:MarkdownTextBlock x:Uid="Oobe_LightSwitch_TipsAndTricks" />
+
+                <StackPanel Orientation="Horizontal" Spacing="8">
+                    <Button x:Uid="OOBE_Settings" Click="SettingsLaunchButton_Click" />
+
+                    <HyperlinkButton NavigateUri="https://aka.ms/PowerToysOverview_LightSwitch" Style="{StaticResource TextButtonStyle}">
+                        <TextBlock x:Uid="LearnMore_LightSwitch" TextWrapping="Wrap" />
+                    </HyperlinkButton>
+                </StackPanel>
+            </StackPanel>
+        </controls:OOBEPageControl.PageContent>
+    </controls:OOBEPageControl>
+</Page>

src/settings-ui/Settings.UI/SettingsXAML/OOBE/Views/OobeLightSwitch.xaml.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.PowerToys.Settings.UI.OOBE.Enums;
+using Microsoft.PowerToys.Settings.UI.OOBE.ViewModel;
+using Microsoft.PowerToys.Settings.UI.Views;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+
+namespace Microsoft.PowerToys.Settings.UI.OOBE.Views
+{
+    public sealed partial class OobeLightSwitch : Page
+    {
+        public OobePowerToysModule ViewModel { get; set; }
+
+        public OobeLightSwitch()
+        {
+            this.InitializeComponent();
+            ViewModel = new OobePowerToysModule(OobeShellPage.OobeShellHandler.Modules[(int)PowerToysModules.LightSwitch]);
+        }
+
+        private void SettingsLaunchButton_Click(object sender, RoutedEventArgs e)
+        {
+            if (OobeShellPage.OpenMainWindowCallback != null)
+            {
+                OobeShellPage.OpenMainWindowCallback(typeof(LightSwitchPage));
+            }
+
+            ViewModel.LogOpeningSettingsEvent();
+        }
+    }
+}