Why Do We Say “Beware The Ides Of March”? March 15 is known as the ides of March. But why do “beware” them? What’s so inauspicious about this otherwise normal day? Why has this humdrum mid-month point become a harbinger of ill fortune? Where did the phrase ides of March come from? First, let’s talk calendars—ancient Roman calendars. Unlike today, the ancient Romans didn’t number their calendar days in order from the first of the month to the last. Instead, they counted backward in relation to three days: the calends, nones, and ides. The calends (or kalends; Latin, kalendae) was the first of the month. Calends, source of the word calendar, is when debts were due. The nones (Latin, nōnae) were the ninth day before the ides. This day was equivalent to the seventh day of March, May, July, and October, and the fifth day of the other months. Originally, the nones corresponded to the first quarter of the moon. The ides (Latin, īdūs) were the fifteenth day of the March, May, July, and October, and the thirteenth day of the other months. The ides originally corresponded to the full moon, storied for its own omens. So, the Roman day of the month was reckoned by counting the days (including the starting and ending days) before the calends, nones, and ides. March 2 was the Latin equivalent of “four days before the nones of March.” March 13 was the equivalent of “three day before the ides of March.” March 27 was the equivalent of “six days before the calends of April.” How did the ides of March become superstitious? The Roman general and statesmen Julius Caesar was assassinated by conspiring senators, notably including Marcus Brutus, on March 15 in 44 b.c. Caesar became a dictator after causing a civil war. His rule, and murder, effectively ended the Roman republic—and changed the course of history. Shakespeare dramatized the assassination (and its aftermath) of Julius Caesar in his eponymous tragedy. Early in the play, dated to around 1599, a soothsayer warns Caesar to “Beware the ides of March.” On this fateful day as he was stabbed (famously 23 times), Shakespeare has the dying dictator say, in Latin, as he recognizes his one-time friend Brutus among the assassins: Et tu, Brute? “You, too Brutus? Caesar probably never said these words. Nor was Shakespeare the first to make them up—though he certainly helped immortalize them, and the ides of March, in culture.