@delgado I think the only way then to do this is offline is to read the computer's clock. I don't think you can do this with vanilla C2, but there is a third-party plugin.
(I'm not sure if it's out of date).
What you'd need to do is save the time before closing it, then saving it to webstorage, then when starting up compare the time now and the old time.
Unfortunately this can be easily cheated by changing the time.