In fact, we used to have 13 months in a calendar year. So why is our calendar 12 months instead? And why did it change? According to the NCESC, there's a long history behind this alteration.

In a scalding-hot argument against the 12-month calendar, a September 1927 issue of The Outlook proclaimed: Momentum behind the International Fixed Calendar, a 13-month calendar with 28 days in ...

Leap years help to keep the 12-month calendar matched up with Earth’s movement around the Sun. After four years, those leftover hours add up to a whole day. In a leap year, we add this extra day ...