in 44 BC, Roman Emperor Julius Caesar was assassinated by high ranking Roman Senators. The day is known as the “Ides of March.”
Caesar summoned the Senate to meet in the Theatre of Pompey on the Ides of March. A certain seer warned Caesar to be on his guard against a great peril on the day of the month of March which the Romans call the Ides; and when the day had come and Caesar was on his way to the senate-house, he greeted the seer with a jest and said: "The Ides of March has come," and the seer said to him softly: "Yes, the Ides of March has come, but it has not passed."
As the Senate convened, Caesar was attacked and stabbed to death by a group of senators who called themselves the Liberatores ("Liberators"); they justified their action on the grounds that they committed tyrannicide and were preserving the Republic from Caesar's alleged monarchical ambitions
What is little known is that every month has an "Ides":
In the Roman calendar, the term ides was used for the 15th day of the months of March, May, July, and October, and the 13th day of the other 8 months..