The Ides of March ("Eidus Martiae" in Latin) is a day on the traditional Roman calendar that corresponds to the date of March 15th on our current calendar. Today the date is commonly associated with bad luck, a reputation that it earned at the end of the reign of the Roman emperor Julius Caesar (100–43 BCE).
According to the Roman historian Suetonius (690–130 CE), the haruspex (seeress) Spurinna warned Caesar in mid-February 44, telling him that the next 30 days were to be fraught with peril, but the danger would end on the Ides of March. When they met on the Ides of March Caesar said "you are aware, surely, that the Ides of March have passed" and Spurinna responded, "surely you realize that they have not yet passed?"
CAESAR to SOOTHSAYER: The Ides of March are come.
SOOTHSAYER (softly): Ay, Caesar, but not gone.
—Shakespeare's Julius Caesar
What Are Ides, Anyway?
The Roman calendar did not number days of an individual month sequentially from first to last as is done today. Rather than sequential numbering, the Romans counted backward from three specific points in the lunar month, depending on the length of the month.
Those points were the Nones (which fell on the fifth in months with 30 days and the seventh day in 31-day months), the Ides (the thirteenth or the fifteenth), and the Kalends (the first of the following month). The Ides typically occurred near a month’s midpoint; specifically on the fifteenth in March. The length of the month was determined by the number of days in the moon's cycle: March's Ides date was determined by the full moon.
Why Caesar Had to Die
There were said to be several plots to kill Caesar and for a multitude of reasons. According to Suetonius, the Sybelline Oracle had declared that Parthia could only be conquered by a Roman king, and the Roman consul Marcus Aurelius Cotta was planning to call for Caesar to be named king in mid-March.
The senators feared Caesar's power, and that he might overthrow the Senate in favour of general tyranny. Brutus and Cassius, the main conspirators in the plot to kill Caesar, were magistrates of the Senate, and as they would not be allowed to either oppose the crowning of Caesar nor remain silent, they had to kill him.
A Historical Moment
Before Caesar went to the theater of Pompey to attend the Senate meeting, he had been given advice not to go, but he did not listen. Doctors had advised him not to go for medical reasons, and his wife, Calpurnia, also did not want him to go based off of troubling dreams that she had.
On the Ides of March, 44 BCE, Caesar was murdered, stabbed to death by the conspirators near the Theatre of Pompey where the Senate was meeting.
Caesar’s assassination transformed Roman history, as it was a central event in marking the transition from the Roman Republic to the Roman Empire. His assassination resulted directly in the Liberator’s Civil War, which was waged to avenge his death.
With Caesar gone, the Roman Republic did not last long and was eventually replaced by the Roman Empire, which lasted approximately 500 years. The initial two centuries of the Roman Empire’s existence were known to be a time of supreme and unprecedented stability and prosperity. The time period came to be known as “Roman Peace.”
Anna Perenna Festival
Before it became notorious as the day of Caesar's death, the Ides of March was a day of religious observations on the Roman calendar, and it is possible that the conspirators chose the date because of that.
In ancient Rome, a festival for Anna Perenna (Annae festum geniale Pennae) was held on the Ides of March. Perenna was a Roman deity of the circle of the year. Her festival originally concluded the ceremonies of the new year, as March was the first month of the year on the original Roman calendar. Thus, Perenna’s festival was celebrated enthusiastically by the common people with picnics, eating, drinking, games, and general revelry.
The Anna Perenna festival was, like many Roman carnivals, a time when celebrants could subvert traditional power relations between social classes and gender roles when people were allowed to speak freely about sex and politics. Most importantly the conspirators could count on the absence of at least a part of the proletariat from the centre of the city, while others would be watching the gladiator's games.