guice

When making this, don't forget that we don't have the option to create new windows.

If you make a timer, you're forced to place it on a currently used window. Not everybody will be keened to that.

Frames required will be anywhere from 2-100, depending on how often and how you want your timer to 'tick'.

Every 30 mins, or 15 mins will take minimal. But when you're talking down to a minute for an hors time, you're getting quite extensive. A case like that I would just suggest getting a small stopwatch to keep next to your computers.

Storing down to a mintue for 30 or 15 minute cycles can be doable, but again implimentation will be tricky.
Also note that spawns aren't on "set timers"
I've timed some at 34:30 others at 27:25 or even just plain 15:00.

But then again, maybe I'm just getting too detailed in this. I'm the kind of guy that plays too close attention to the details. I guess that's why I'm a programmer.