By: Alexandra Wenger ‘21
Everyone knows the old verse, “Thirty days hath September, April, June, and November. All the rest have thirty-one, except February, the shortest one.” Perhaps you know the variant with the ending, “except February, which has twenty-eight, dear, but twenty-nine in a leap-year!” Either way, the message is the same: not all of our months have the same number of days. Why is that? Who decided that was a good idea? The answer lies in the origin of our modern-day calendar, or the Gregorian calendar.
The Gregorian calendar is based on the Julian calendar, and the Julian calendar, in turn, on the Roman calendar. Ancient Romans based their concept of a month on the cycle of the moon. However, the lunar cycle does not divide evenly into the 365.25 days in a year. To remedy this, ancient Roman calendars had months that were 29 or 30 days, with 10 months in a year. Approximately 60 days were still unaccounted for, so the months Januarius and Februarius were added. This was the Roman calendar.
The Julian calendar, a modification by Julius Caesar of the Roman calendar, adjusted each month to 30 or 31 days, with the exception of Februarius. Februarius had 28, and an extra day added each fourth year. Thus, our year has 365.25 days, because each leap year has 366 days.