Suppose you're adding features to a site that stores times in local time. You're trying to calculate how many hours it's been since Nov 4, 2007, at 1:30am Eastern. You have to ask the question, Which 1:30am is it? The 1:30am before the clocks rolled back, or the one after?
Suppose a user enters a date and time of Mar 11, 2012, 2:14am. You'd have to return:
ERROR: Time does not exist.
Daylight Savings Time is stupid.
