Do you ever have strange thoughts during the time between wakefulness and sleep? I was in bed last night, drifting down into the warm pillows of sleep, when my mind started fussing about the number of days in a month. Why aren’t there an equal number of days in each month? It suddenly seemed exceedingly strange that some months had 30 days, others 31, and poor February gets only 28, except every leap year when it gets an additional day. My mind wanted to do the math: 365 days in a year divided by 12 months and I fell asleep.
This morning, I’m back to the math. The answer is 30.416666, or 30.42. OK, I guess whoever developed our calendar decided that we could do without fractional days. So now we have the days divided up thusly:
January = 31 days
February = 28 days (except leap year when it has 29)
March = 31
April = 30
May = 31
June = 30
July = 31
August = 31
September = 30
October = 31
November = 30
December = 31
My curiosity has gotten the better of me today. I have to solve this mystery. Why this configuration? Why not give February 30 days and take one each away from two of the 31-day months?
As I’ve been researching this question online this morning (thank you, Wikipedia), I’ve learned that before our modern calendar, other calendars existed. Each ancient civilization developed its own calendar, usually based on the lunar cycle for the months. The number of days in each year varied. The Vikings based their calendar on important activities: Harpa-month, lamb-fold-time, sun-month, midsummer, hay-month, harvest-month, slaughtering-month, “Ylir,” ram-month, thorn-month, Goa-month, and last-month-of-winter. Both the Sumerians and the ancient Greeks had calendars similar to our modern one. The Mayan and Mesoamerican calendars are the most complex, and frankly, I’m not sure how they kept track of what day it was.
Our modern calendar evolved from the calendar that Julius Caesar developed during his third consulship. The Julian calendar had a year of 365.25 days divided into 12 months, with a leap year adding a day every four years. Sound familiar? Old Julius kept the names of the months that had been used by the old Roman calendar but altered the number of days for each month to:
Ianuarius (January) = 31 days
Februarius (February) = 28 days (29 for the leap year)
Martius (March) = 31 days
Aprilis (April) = 30
Maius (May) = 31
Iunius (June) = 30
Quintilis (Iulius = July) = 31 days
Sextilis (Augustus = August) = 31 days
September (same) = 30 days
October (same) = 31 days
November (same) = 30 days
December (same) = 31 days
Look familiar? Julius Caesar’s calendar, the Julian, remained in effect in Europe until 1582 when Pope Gregory XIII decided he wanted to mess with it. Pope Gregory needed to reform the calendar because the accepted length of the year, 365.25 days, did not take into account that the actual length is 11 minutes shorter. Those minutes add up over time, and the good Pope wanted to fix the dates of the equinoxes. The Gregorian calendar takes into account these 11 minutes, and also reforms the lunar cycle used by the Catholic Church with the Julian calendar to calculate the date of Easter. His reform of leap years gave us our present system for calculating them: “Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100; the centurial years that are exactly divisible by 400 are still leap years. For example, the year 1900 is not a leap year; the year 2000 is a leap year.” Pope Gregory XIII did not change the number of days per month used in the Julian calendar.