What are the Ides of March?

Three fixed days a month

Romans did not number the days of a month from 1 to 31. They counted toward three landmarks. The Kalends, Kalendae, was the first day. The Nones, Nonae, fell on the 5th, and the Ides, Idus, on the 13th. In four months, March, May, July and October, the Nones and the Ides came two days later, on the 7th and the 15th. That is why the Ides of March is March 15.

Every other day was counted backward to the next landmark, and Romans counted both ends. March 14 was pridie Idus Martias, the day before the Ides of March. March 12 was the fourth day before the Ides: the 12th, 13th, 14th and 15th. Once the Ides had passed, the count ran on toward the Kalends of April. The Nones got their name the same way. They were the ninth day before the Ides, counting both days.

Why the middle of the month

The landmarks go back to a calendar that followed the moon: the Kalends came with the new crescent, the Nones with the first quarter, the Ides with the full moon. A junior priest watched for the new moon and called out how many days were left until the Nones. From calare, “to call out,” came Kalendae, and from the Kalends came our word calendar, through the account books in which Romans recorded debts that fell due on the first of the month. What Idus meant was already a puzzle in antiquity. Macrobius, writing in the fifth century AD, traced it to an Etruscan verb meaning “to divide”: the day that splits the month in two.

Every Ides belonged to Jupiter. His priest led a sheep, the ovis Idulis, up to the citadel on the Capitol to be sacrificed. The Ides of March had a party of its own as well, the festival of Anna Perenna, goddess of the year. Ordinary Romans picnicked beside the Tiber and, Ovid says, drank as many cups as the years they hoped to live. March had once been the first month of the year, and from 222 to 154 BC the consuls took office on the Ides of March.

“Beware the Ides of March”

Suetonius tells the warning. At a sacrifice, the soothsayer Spurinna, a haruspex who read the future in the organs of animals, told Caesar to beware a danger that would come no later than the Ides of March. On the day itself Caesar passed him on the way to the Senate and joked that the Ides had come and he was still unharmed. Spurinna answered that they had come, but not gone. Plutarch tells the same exchange without naming the seer.

Shakespeare turned it into four words. In Julius Caesar (1599) a soothsayer calls out of the crowd, “Beware the ides of March,” and Caesar waves him off as a dreamer. In the third act they meet again: “The ides of March are come.” “Ay, Caesar; but not gone.”

What happened that day

That same day, senators led by Brutus and Cassius stabbed Caesar to death in the hall beside Pompey’s theater (how Julius Caesar died). The killers were proud of the date. Brutus put it on his silver coins, shortened to EID MAR, between two daggers.

The phrase today

Ever since, the Ides of March has meant a day of reckoning, a deadline that looks harmless until it arrives, and every March 15 headlines borrow it. The other landmarks left their mark too. Augustus, Suetonius says, liked to say that people who would never pay their debts would pay on the Greek Kalends. The Greek calendar had no Kalends at all.