In the United States, Friday the 13 is known as an “unlucky” day by superstitious people. Another famously unlucky day for some is March 15, also known as, “The Ides of March.” The Ides of March is so unlucky that it is often spoken as a warning: “Beware the Ides of March.” First, what exactly is an “ides?” The Latin root of “ides,” a singular word, means “to divide.” So, the ides of any month falls in its middle. The Roman calendar set ides on the 15th in March, May, July and October or on the 13th in the other months. The ides of a month usually falls on the first day of a full moon. In Roman times, the Ides of March was known as a date for paying off debts. But this connection was quickly lost because of different timing between calendar months and changes in the moon’s appearance. The Ides of March was also a time people celebrated Mars, the god of war. But why do some people still use the expression, "Beware of the Ides of March"? Why do they consider it an unlucky day? March 15 was very unlucky for one man a very long time ago. On that date in the year 44 BC Julius Caesar was killed.