How do I create a simple virtual pet timer?

I understand all the variable settings to make a virtual pet type app, but I'm stuck on how to have the app check the users local clock/time to compare the amount of time since the last usage. I need this function to not only make the variables like hunger and happiness more realistic but to also allow a "lifespan" type counter.

I also have no idea how to save on exit.. I imagine I can make a "on browser close>save game" sort of thing happen but I haven't gotten there yet.

thank you!

Try this plugin:

Try this plugin:

I'll try that, thank you!

Do you know if there is a way to do it without a plugin? I've yet to try new plugins but this looks pretty solid if I can't do it with stock C2.