The US is also differnt in the fact that it uses the format mm-dd-yy instead of far more common dd-mm-yy
Arg, *both* of those drive me crazy. yyyy-mm-dd, people!

The calendar is a crazy one. It's pretty much fudged (as you know) to correspond to the Earth's rotation around the sun. Hence, the every-four-year leap year to keep it working. I heard somewhere once (and can't verify it) that every century will need a Febuary 30th to pick up the accumulated slack. Can any of you guys verify this?
That doesn't sound right to me. Based on the current rules, if a year is divisible by 100, it's *not* a leap year, unless it is also divisible by 400. So in three centuries out of four, you would actually not have a Feb 29 when you "normally" would. So 2000 was a leap year, since it was divisible by 400, but 1900 wasn't, and 2100 won't be. So it doesn't make sense to me that we'd somehow need to add an "extra" extra day somewhere... why wouldn't we just keep all years divisible by 100 as a leap year?
But then, I've been wrong many, many times before...
