The Ides of March

Today is the Ides of March, made famous to us moderns by William Shakespeare in his play Julius Caesar. The Ides of March is the day when Caesar's was assassinated in 44BC.

Caesar: Who is it in the press that calls on me?
I hear a tongue, shriller than all the music
Cry "Caesar!" Speak. Caesar is turn'd to hear.

Soothsayer: Beware the ides of March.

Historically, it is the date by which debts were usually settled (including, apparently, Caesar's).

Perhaps it was the ancient version of our present-day ides of April.