Landon Dyer has a nice rant on date/time calculation over on his blog:

This is a class of problem that everyone knows is trivial. “Of course I know how to do this,” you probably think to yourself, “This is trivial, I can just code this thing up and have an early lunch.” Trivial is the most dangerous word in all of computerdom, it’s a misprounciation of “Evil”. Your blood should run cold if you hear it spoken out loud, because the Gods will be listening carefully and taking notes on how to screw you if they ever hear you say it.

The comments make this article even more interesting with everyone comparing their date/time war stories.