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Easter is a moveable feast whose date can fall anywhere from March 22 to April 25, depending on the year. Easter falls on the first Sunday after the first Full Moon in (a northern hemisphere) spring. With spring beginning on the March 20th equinox, the first Full Moon of spring is the one occurring on or after this date. If the earliest springtime Full Moon - the Paschal Full Moon - falls on a Sunday, then Easter comes on the following Sunday.
This year, the March equinox arrives on Thursday, March 20, at 5:48 Universal Time (1:48 a.m. Eastern Daylight Time). The March Full Moon falls on Friday, March 21, at 18:40 Universal Time (2:40 p.m. Eastern Daylight Time). For Easter to come as early as March 22 or 23, the equinox and the Full Moon have to come toward the end of the week. But there has to be enough wiggle room between the March equinox and Sunday for the Full Moon to squirm in between the two.
Such a sequence is hard to muster. As a matter of fact, Easter Sunday falls on March 23 only once in the 21st century. The last time Easter occurred on March 23 was in 1913, and the next time won't be till 2160. As for March 22 Easters, the last one occurred in 1818 and the next one will be in 2285. Incidentally, Easter Sunday cannot occur in March two years in a row.
The closest years for an April 25 Easter - the latest possible date for Easter Sunday - are in 1943 and 2038.
Ecclesiastical versus Astronomical Easters
My explanation of the methodology used to determine the date of Easter was purposely oversimplified. The equinox and the first Full Moon of spring - the Paschal Full Moon - are based on ecclesiastical tables, not the astronomical times of the spring equinox and Full Moon. For instance, the ecclesiastical spring equinox is fixed on March 21, but the actual spring equinox falls on either March 19 or 20 for the remainder of the 21st century.
If there's a discrepancy, an ecclesiastical Easter trumps an astronomical Easter. This happens 7 times in the 21st century: 2038, 2049, 2069, 2076, 2089, 2095 & 2096.* For a fuller discussion on the subject, see this US Naval Observatory page.
*page 365 of Mathematical Astronomy Morsels by Jean Meeus
copyright 2008 by Bruce McClure
|Easter Dates 1700 to 2299|
February 2008 Feature * April 2008 Feature