Beware

Today is the Ides of March. Be careful. Be very careful. Learn from history.

SOOTHSAYER: Beware the ides of March.
CAESAR: What man is that?
BRUTUS: A soothsayer bids you beware the ides of March.
CAESAR: Set him before me, let me see his face.
CASSIUS: Fellow, come from the throng, look upon Caesar.
CAESAR: What say'st thou to me now? Speak once again.
SOOTHSAYER: Beware the ides of March.
CAESAR: He is a dreamer, let us leave him. Pass.
[Sennet. Exeunt all except Brutus and Cassius.

Remember what happened next?

In earlier times, it was a day dedicated to the god Mars.