While the minimalist, neat freak, wishing-I-lived-in-a-Shinto-shrine part of me agrees completely with anonymous and jdporter, the reality is that most humans aren't like me. Therefore, it is my belief, that even when we have space-based nations, and these space-based nations become economically dominant, the common rustic person on Earth will still use time zones. And, of course, there will be some American-descended space-based nation that refuses to convert to metric time like the rest of the solar system.
What bothers me now however, is why does a new "day" start in the middle of the night? Shouldn't 00:00 be the time when the sun rises during the Spring/Fall equinox?