March 15th is the Ides of March. Why do we still hear people say, "Beware the Ides of March"? Well, we have William Shakespeare to thank for that!
In Shakespeare's well-known play Julius Caesar, Caesar is walking in the street with his fellow Roman senators when suddenly a Soothsayer (aka: a fortune teller) says, "Beware the Ides of March!" Caesar disregards the warning, but we know he is making a mistake!
The next day, Caesar is on his way to the Senate. He sees the Soothsayer and says, "The Ides of March are come." The Soothsayer replies, "Aye, Caesar, but not gone." A short while later, Caesar is ambushed and killed by his enemies in the Senate.
Shakespeare invented the scene with the Soothsayer, but the idea that we should beware the "Ides," the 15th of March, has remained part of our popular culture. So, what are the Ides?
Ancient Romans used a calendar in which they had to figure out what a date was by knowing how far it was from three named dates each month. The first day of the month was always Kalends. You might say, "Meet me for lunch on the 2nd day after Kalends."
The Nones was the next named date, which fell on the 5th day in some months, and the 7th in others.
Finally, every month had an Ides. In March, May, July, and October, it was the 15th day. In all the other months, the Ides fell on the 17th.
We can be very glad that before he died, Julius Caesar simplified the Roman calendar. His Julian calendar corrected many problems and led the way to the modern Gregorian calendar. So, while we really don't need to beware the Ides of March, Shakespeare certainly made it an interesting date to remember!