What in Blazes Are the Ides of March?

A lighthearted romp through treachery, betrayal, and murder

Joseph Finder got me interested in the Ides of March, a date that Julius Caesar immortalized by being murdered on it, leading many centuries later to Shakespeare’s famous warning “beware the Ides of March.” It falls today, March 15 (except not really — keep reading), and conjures up all manner of things, from blood moons to the calendar to springtime rites to mysterious people from the ancient shores of the Tyrrhenian Sea.

(Finder, by the way, is a master author, most recently of The Oligarch’s Daughter: A Novel, which I’ve just started reading. It’s a page turner, probably more engaging than this post of mine, but please don’t let that stop you from reading on.)

The Moon and the Sea

The Ides was originally the “full moon,” long before March was March.

The English word Ides comes from the Latin word Idūs, which, in turn, is “possibly of Etruscan origin.” That is to say, scholars don’t know where it comes from. But that’s fair, because they also don’t know entirely who the Etruscans were. They were important though. They appeared out of nowhere on the shores of the Tyrrhenian Sea with sophisticated writing, advanced art, considerable societal organization, skilled traders, unparalleled equality between men and woman, and an advanced military. The Etruscans bestowed many of their gifts on a local tribe before disappearing as mysteriously as they arrived. The local tribe became the all-mighty Rome.

How to Count to One

These Romans reckoned the month differently than we do. We count forward from the beginning. They counted backward from the end, or, rather, from three ends.

The Romans counted backward from the end.

The first end was conveniently also the beginning, the new moon, the first day of the month, denoted the Kalends (Kalendae). But it was the end of the Kalends period. Therefore the last day of the month was the “Day Before the Kalends” (pridie Kalendas); the day before that was “Three Days Before the Kalends” (ante diem III Kalendas) — and yes, it was three days before, not two days before, because the day of the Kalends was reckoned in the counting as day one, there being no possibility at that time of zero days before anything because the concept of zero was still in its infancy.

The second end was the Nones (Nonae), or first quarter of the moon. And it worked the same way. The second day of the month was therefore “Seven Days Before the Nones” (ante diem VII Nōnās).

The third end was the now-famous Ides (Idūs), the full moon. (Confusingly, it takes one week to go from new moon to quarter moon, but also only one week to go from quarter moon to full moon. How’s that for new math?)

Gradually the Roman lunar calendar incorporated elements of a solar calendar, and the months were given fixed lengths. Under this system, The Nones and Ides were standardized as the 5th/13th days of the month for most months, or as the 7th/15th days for four of the months, including March. This is why March 15 is the Ides of March. (Again, though, not really; and again, keep reading to see why.)

Brutality

A quick note: Caesar was murdered by his trusted friend Brutus (leading to Shakespeare’s famous accusation: “et tu Brute,” even you, Brutus.)

The English “brute” stems from the Latin brūtus, with roughly the same meaning; and the English “brutality” veered off from the same root to assume a more sinister meaning. But the connection between Brutus the brutal assassin and brūtus the Latin adjective appears to one of coincidence. Now back to our story.

The Full Moons of Spring

Having been standardized, March 15 is no longer necessarily the full moon; but this year, 2025, it came very close. And this year we also had the glory of a true blood moon, a full lunar eclipse. (Lunar eclipses can only happen on full moons.)

The Ides, or full moons, of early spring are magical times around the world and among the world’s cultures, anchoring such holidays as Holi (a colorful Hindu festival celebrating the victory of good over evil), Purim (a festive Jewish holiday also celebrating the victory of good over evil), the Chinese Lantern Festival (celebrating light over darkness), Madhu Purnima (a Buddhist festival of generosity and harmony), and others, to say nothing of the Jewish Passover (celebrating freedom and renewal) and the Christian Easter (celebrating renewal and redemption). Bummer for Caesar that he was murdered on the Ides.

But as I’ve said twice now, March 15 isn’t really the Ides of March, or, rather, our March 15 isn’t. That’s because the megalomaniac Julius Caesar actually created his own calendar. Until Caesar, the Roman calendar had been lunar and solar, with not enough days in the year, and therefore with the periodic insertion of an extra month (Mercedonius) to make sure the Roman harvest festivals fell during the Roman harvests.

The Sun

Caesar wrested control of the calendar from the fixed lunar cycles and finalized the solar calendar. He also renamed a month after himself: July. (July had previously been called Quintilis, from “five.” Now it’s the seventh month but the year used to begin in March. See above for all the happy March things.)

The calendar Caesar inherited had drifted out of sync with the sun, because the extra months had long been neglected. To readjust things, in 46 BCE Caesar created a year of 445 days — appropriately called the annus confusionis (“Year of Confusion”). Two year later he would be murdered on the Ides of March of his new calendar.

But his calendar — the “Julian Calendar” — wasn’t perfect either. It, too, drifted out of sync with the sun. This was a big problem for the Church, because of Easter. Easter is scheduled with the last remaining hint of lunar-calendarness: it conveniently falls on the first Sunday after the first full moon on or after the spring equinox. But Easter has to be in the spring, and, because of the minor inaccuracies of the Julian Calendar, Easter had been marching forward into summer over the centuries.

Lunacy

Amid all this craziness, and with one more blow to come, it’s worth reviewing a recurring theme. Our saga underscores our battle with nature: Does the moon decide when the month starts or do we? What about the year? Do the months have names? Do the days of the week? (Curiously, in the monotheistic West the names of the days pay homage to Pagan gods.) Who decides where countries begin and end, leaders, or rivers and mountains? Does the past exert an influence over the now?

More generally, how do we order our world?

We may feel that we have outgrown childish influences like the moon, but maybe not: the word “lunacy” after all comes from the Latin lūnāticus, “moon struck.”

At any rate:

The Pope

Pope Gregory in the 16th century fixed Caesar’s calendar, giving us the calendar we use today (well, many of us): the Gregorian Calendar. To get things back on track, His Holiness lopped ten days off of an October; in 1582, the day after October 4 was October 15. And to keep things on track, he also changed the leap-year policy moving forward.

But even though we use the Gregorian Calendar today, don’t you think we owe it to old Julius Caesar to use his calendar to mark his own death on the Ides of March? I do. And his Ides of March, March 15, falls on what we now call March 28. So mark your calendar now. The Ides of March are coming up.

Beware.