diff --git a/asciinema/asciicast/v2.py b/asciinema/asciicast/v2.py
index 8a0502f..ecd196c 100644
--- a/asciinema/asciicast/v2.py
+++ b/asciinema/asciicast/v2.py
@@ -93,6 +93,7 @@ class Recorder:
             'version': 2,
             'width': cols,
             'height': lines,
+            'timestamp': int(time.time()),
             'env': saved_env,
             # TODO save max_wait here
         }
diff --git a/doc/asciicast-v2.md b/doc/asciicast-v2.md
index 8930fd3..5cde9d9 100644
--- a/doc/asciicast-v2.md
+++ b/doc/asciicast-v2.md
@@ -30,6 +30,7 @@ The following meta-data is **required** in asciicast v2:
 
 The following meta-data is **optional** in asciicast v2:
 
+* `timestamp` - Unix timestamp of the beginning of the recording session (integer),
 * `duration` - duration of the whole recording in seconds (when it's known upfront),
 * `command` - command that was recorded, as given via `-c` option to `asciinema rec`,
 * `title` - title of the asciicast, as given via `-t` option to `asciinema rec`,