A Moment of Science
Calendar Science and April Fool's Day
None of our modern serious religions would ever invent such a wonderful holiday as April Fool's Day. But the Catholic Church, it turns out, played a role in it.
Although there is considerable doubt, April Fool's Day appears to have begun when the calendar reforms of Pope Gregory XIII were instituted in 1582. Although under the Julian calendar instituted in 45 BCE by Caesar the New Year began on January 1st, for many centuries England and most of Europe observed New Year's Day in the spring, beginning on March 25th and continuing through April 1st. Unfortunately, the Julian Calendar was off by a bit more than 11 minutes a year. So that by the 16th Century the spring equinox fell 10 days earlier than it should, on March 11th, and the Winter Solstice was falling on December 11th.
So the Pope decreed that ten days in October, 1582, should not be counted, the 4th of that month being immediately followed by the 15th. Also, leap years were in future to be omitted in centennial years not exactly divisible by four in order to keep the problem from recurring. In addition, New Year's Day was fixed on January 1st. It is interesting that with respect to this problem, the Vatican functioned as a kind of international body. It was too much to expect that all the individual rulers would cooperate voluntarily in those days.
Still, France and other predominantly Catholic countries adopted the new calendar immediately but Germany and other predominantly Protestant states kept the old system in place until 1700. England — and its American colonies — waited until 1752 to adopt the reform. April Fool's Day came in as a result of the fact that even when national governments officially adopted the new Gregorian system, some people insisted on continuing to observe the old ways, including the New Year's celebrations of April 1st.
It seems that the nonconformists probably disliked the source of the change: the Catholic Church and the Pope. But even with this element involved, most people adopted the change because it was clearly necessary and sensible. And those who objected were considered fools and made the butt of jokes and pranks. Today most people might even consider it foolish to suppose that the calendar has anything to do with religion.