When I run
gsettings get com.ubuntu.update-manager launch-time the response is
1382579402. What does the value of
That's presumably a time in Unix epoch format, i.e. seconds since 01/01/1970 UTC. It tells you when update manager last ran (see e.g. here).
You can display it in a more user-friendly way with the
To get the current time in that format: