Blame/credit the 5th Century B.C. Greeks.
Plus, thus began the Wobbly AFL-CIO History Mongers, ya gotta problem
with that?
For instance, they're for:
Doubletime for teaching on international holidays.
I can't think of any either, perhaps May 1st: No, that's Communists &
dentists fun day.
http://www.tnr.com/politics/story.html?id=c0c23dea-f39d-43e9-a6bd-29435335a6a4