"Beware the Ides of March!"Ides: the fifteenth day of March, May, July, and October, and the thirteenth day of the other months. Julius Caesar was assassinated on the Ides of March – March 15, 44 B.C. Today, this warning is best known from William Shakespeare's play, Julius Caesar. The word "ides" was derived from the Latin "to divide". The "ides" were originally meant to mark the full moon - but since the solar calendar months and lunar months were of different lengths, the "ides" quickly lost their original intent and purpose, according to this article.