Easter - a moveable feast

Easter is a moveable feast, but not as moveable as it used to be. In fact it was drifting alarmingly summerwards in medieval times, until the Pope of the time, Gregory XIII, did something about it. More of which later. Early Christians couldn’t decide when to celebrate Easter. It was known that Christ’s Last Supper was enjoyed on or around Passover: some celebrated his resurrection at the same time as the Jewish festival, others on the following Sunday. In order to get everyone singing from the same hymnbook, in 325 The Council of Nicaea decided that the Christian festival should be celebrated on the Sunday after the first full moon after the Spring equinox, adjudged to be March 21st.

All well and good. The problem was that the Julian calendar’s ‘leap year’ solution to making such lunar-related dates stay in the same season only worked so well: by the late 16th century, the true vernal equinox was occurring more than a week before March 21st.
In stepped Gregory with his solution: he knocked ten days out of the calendar in 1582 (the 5th to the 14th October didn’t exist and tough if it was your birthday) and announced that future leap years for every year that is divisible by 100 would be abolished, except those divisible by 400. 2000 had one, then, but 1900 didn’t, and neither will 2100.
It was a pretty good solution, although it’s not completely precise (we’ve tested your patience enough as it is to explain any further). The Greek Orthodox church, by the way, celebrates Easter according to the Julian calendar: it can take place as long as five weeks after the Vatican’s date. AG