well that make me think about -- when does a day start?
as faldage pointed out, we used to use the old style, still use by the Jews, that a day ended at sundown, and the you then had Monnight, (sundown to dawn, and Monday, dawn to sunset)

Now we end the day in the middle of the night. How about other cultures? is there anywhere that the day starts at dawn? Monday, followed by Monnight? is suspect not, since i think the old style was something christianity borrowed from the jews, and i suspect moslems did too. but what about cultures that were not exposed to the judeo/christian concepts?