The Ides of March are nearly upon us...

The idea that March 15 (or "the ides of March") is unlucky goes back to ancient traditions and superstitions. Most people have probably heard the phrase "the ides of March" quoted from a famous line in Shakespeare's play Julius Caesar: "Beware the ides of March." The phrase, spoken twice by a soothsayer, warns Caesar of his impending assassination.

The Ides of March was certainly unlucky for Caesar, who actually was killed on that day. (Of course these days a psychic making such a death threat would be investigated by the Secret Service.) Since that time the idea stuck that the Ides of March is unlucky or a portent of doom—even if your name isn't Caesar.

The fact that an aura of doom stuck to the date through millennia is not surprising. People tend to give special significance to certain dates: birthdays, anniversaries, leap years, Friday the Thirteenth, and so on. This tendency is similar to numerology, in which people interpret cosmic significance in numbers and dates, seeing them as good or bad, lucky or unlucky. July 7, 2007, for example, was supposedly "extra lucky" because the numerical date was full of lucky sevens.

If the bad luck story is true, presumably an Ides of March that falls on Friday the Thirteenth would be incredibly unlucky. Fortunately, it is very rare, and only occurs four times out of over 5,000 dates on the perpetual calendar. The next one won't happen until 2013, so we have time to prepare.

Of course there is no objective reality to lucky or unlucky dates. What can sometimes happen is that people will come to believe a date is "bad" or unlucky and will focus on anything that goes wrong on that day. In that way, it becomes kind of a self-fulfilling prophecy: You assume you're going to have a bad day, and so you do.

Ides, in case you're wondering, are a relic of ancient Rome. Ides were days of settling debts (occurring on the fifteenth of March, May, July, and October, and on the thirteenth of the other months.) So if you really want to carry on this tradition, wait until the next Ides and tell your deadbeat friends, "Pay up, dude. It's the ides of June."

Benjamin Radford is managing editor of the Skeptical Inquirer science magazine. His books, films, and other projects can be found on his website. His Bad Science column appears regularly on LiveScience.