The founder of Rome, Romulus, is believed to have created a calendar containing ten months. The year had started in March, which explains why September, October, November and December are named after the Latin word for seven, eight, nine and ten. (septem is Latin for 7, octo is 8, novem is 9 and decem is 10).
It was Julius Caesar who changed the calendar to be similar to the one we recognise today, with the addition of two months at the start of the year, January and February; making 365 days in a year, and the introduction of “leap years” every fourth year.
Some of the months of the year were named after Roman gods:
After their deaths, the months of July and August were named after Julius Caesar and Emperor Augustus.
There were special names for three specific days in each month. The system was originally based on phases of the Moon:
People talked in terms of the number of days before or after Kalends, Nones or Ides.
Julius Caesar was warned to "Beware the Ides of March", which was proven true as he was murdered on March 15th.