March 15th is known as the Ides of March in the Roman calendar. This date is significant because it marks the deadline for settling debts in ancient Rome. It was also a time for various religious observances and festivals. In 44 B.C., March 15th became infamous as the day of the assassination of Julius Caesar. He was killed by a group of Roman senators who feared his growing power. This event has been immortalized in literature, particularly in William Shakespeare's play "Julius Caesar," where the phrase "Beware the Ides of March" is famously uttered.