Sunday, March 23rd is Easter for western churches. It’s the earliest Easter since 1913. The last time Easter fell at an earlier date was in 1818, when it fell on the 22nd. Since then it’s fallen on the 23rd 3 times in 1845, 1856 and 1913. It will not do it again this century. The formula for calculating the Easter date was codified at the church Council of Nicaea in 325. Basically stated Easter falls on the first Sunday after the first full moon of spring. The start of spring or vernal equinox was fixed as March 21st. That’s the same assumption the church uses today. Astronomically this year spring starts on the 20th, and the first full moon is on the Friday the 21st and Easter falls 2 days later. Back then the calendar devised by Julius Caesar was used in the Roman world. We call it the Julian Calendar. It was a straight forward calendar with three normal years of 265 days and a fourth of 366 days, a leap year added to approximate the nearly 365 1/4 day tropical (seasonal) year.
By the 16th century the leaders of the Roman Catholic church were becoming dismayed at the departure between the Ecclesiastical vernal equinox, set at March 21st, and the astronomical vernal equinox which was than occurring around March 11th. That meant that Easter, a spring feast was slowly migrating to summer by nearly a day every century. A commission was set up to fix the problem. The solution came in two forms. First, 10 days would be deleted from the calendar to bring the astronomical and ecclesiastical vernal equinoxes back into rough agreement. Second, century years, normally leap years in the Julian calendar would be ordinary years unless they were divisible by 400. By this formula the year 2000 was a leap year while 1900 was not, despite what Microsoft Excel tells you. This is the Gregorian calendar we use today.
The original reason for the Easter formula set out in Nicaea in 325 A.D. was to use the Roman Julian calendar, based on the sun, to locate Easter close to Passover which used the lunar Jewish Calendar. That worked pretty well until the Gregorian reform of 1582. Now Easter in western churches follows Passover only about half the time. This year’s early Easter is a full month before Passover and Eastern Orthodox Easter. The Eastern Orthodox churches still use the Julian Calendar, and the reason they’re still in sync with Passover is because full moon dates repeat every 19 Julian Years. It’s called the Metonic Cycle. This year Passover begins at sunset April 19th. Orthodox Easter then occurs on April 27th. These are Gregorian calendar dates. Whichever Easter is yours, have a happy one.
Tags: Events, History by Bob Moler
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