Today is the Ides of March, famous largely because Julius Caesar was assassinated on this day in 44 BC by his enemies in the Pompeii Theatre, where the Roman Senate was meeting. He had been warned in early March about some danger that would befall him no later than the Ides of March by Titus Vestricius Spurinna, an Etruscan haruspex (soothsayer or astrologer). Caesar encountered Spurinna on the way to the Senate on the 15th of March and made fun of him saying “The Ides of March are come”, to which Spurinna replied “Yes, they are come, but they are not past.” Caesar should have heeded these words because later that day he was assassinated by his enemies. But he didn’t. Oh well. (At least it gave Shakespeare something to write about.)

But what are the “Ides” exactly?

This goes back a couple of thousand years or so when the Roman calendar was based on three important days: the Kalends, the Nones and the Ides.

The Idūs (Ides) was the 13th or 15th day of the month, depending on the month, and was likely the day of the full moon when the months were more closely tied to the lunar cycle.

The other special days in the month were the Kalendae (Kalends), the first day of the month, and Nonae (Nones) on either the 5th or 7th day of the month, which was the probably the half moon.

The other days weren’t numbered, but rather referred to by how many days before the Kalends, Nones or Ides.

There’s a little poem I found in Wikipedia to help remember which months had the special days:

In March, July, October, May

The Ides fall on the fifteenth day

The Nones the seventh; all besides

Have two days less for Nones and Ides.