That was in 44 B.C. And, to this day, March 15 is still considered a fateful day.
The saying, "Beware the Ides of March," was popularized by William Shakespeare's play, "Julius Caesar,"
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.
Caesar: What man is that?
Brutus: A soothsayer bids you beware the ides of March.
From that moment forward, March 15 became associated with Caesar's assassination at the statue of Pompey by Roman senators, including his once-close friend, Brutus. That led to another famous Shakespeare quote, "Et tu, Brute?"
"Beware the Ides of March" is still recognized as a warning.
Before Caesar's assassination, the Ides of March was related to the phases of the moon for the Roman calendar.