"Beware the Ides of March" is a well-known quote from Shakespeare's Julius Caesar. This was a warning of his impending death. But the Ides have many references aside from this most famous Shakespeare Line. The Ides of March originate from religious observances and in Roman times, was a deadline for settling debts.
In Ancient Rome, the months of the calendar had an Ides. The Ides are actually every month and divide the month in half. The Ides fell on the 15th day of March, May, July and October and on the 13th day of all other months. Interestingly, more people relate the number 13 to bad luck, but thanks to Shakespeare, the Ides of March is the unlucky Ides.