You've probably of heard the soothsayer’s warning to Julius Caesar in William Shakespeare's play of the same name: “Beware the Ides of March.” Not only did Shakespeare’s words stick, they branded the phrase—and the date, March 15—with a dark and gloomy connotation. It’s likely that many people who use the phrase today don’t know its true origin. In fact, just about every pop culture reference to the Ides—save for those appearing in actual history-based books, movies or television specials—makes it seem like the day itself is cursed.
But the Ides of March actually has a non-threatening origin story. Kalends, Nones and Ides were ancient markers used to reference dates in relation to lunar phases. Ides simply referred to the first full moon of a given month, which usually fell between the 13th and 15th. In fact, the Ides of March once signified the new year, which meant celebrations and rejoicing.