I'm going to (quietly and without strong emphasis) defend Date::Calc. I've used it on many occasions and found it to be very helpful. But, then again, I never did anything wonky with it. Mostly, it was for date offsets and I wrote my own object around it. *shrugs* Having it on hand was nice cause DateTime didn't exist yet. Now that it does, I'll probably switch. But, for the nonce, it is still on my list of modules to install whenever I build a new dev server.