The ides of March is a date made infamous by the assassination of Julius Cesar in 44 BC.
It was marked by the Romans with a series of religious observances and simply meant the full moon of the month – which in this case was March 15th.
The Roman calendar had three significant markers each month that were dictated by the phases of the moon:
Kalends; the 1st day of the month and the day of the new moon
Nones; the 5th or 7th of the month and the day of the half moon
Ides: the 13th or 15th of the month and the day of the full moon
Cesar had been warned by a number of signs and then finally by a soothsayer that his death would occur before the ides – and had debated not attending the Senate that day, but decided to journey in and was then stabbed to death.
Despite Cesar’s death, it wasn’t until Shakespeare’s production of ‘Julius Cesar’ in 1601 that the ides of March became associated with danger when the soothsayer warned Cesar to ‘Beware the Ides of March’.