NORFOLK, Va. — Have you ever wondered why Easter is on a different Sunday each year? Easter is a “moveable feast,” and its date is determined by something called the “computation,” or computus in Latin.
The holiday occurs on the Sunday after the first full moon that follows the vernal (spring) equinox, which begins spring in the Northern Hemisphere.
Because the lunar calendar is always 29 ½ days and the Gregorian Calendar is not in sync, Easter can be any Sunday from March 22 to April 25!
The last time Easter Sunday fell on March 22 was in 1818, when the full moon fell on March 21. That won’t happen again until 2285.
And in 1943, the full moon fell on March 20, just before the equinox. The next full moon was on a Sunday, April 18. That made the next Sunday -- April 25 -- Easter Sunday. That won’t happen again until 2038.
Of course, not all Christians celebrate Easter on the same Sunday. Catholic and Protestant churches use the Gregorian Calendar to set the date, while Eastern Orthodox churches use the Julian Calendar.
The date of Passover also changes from year to year on the Gregorian Calendar. However, it always starts on the 15th day of the Hebrew month of Nisan, the first month of the Hebrew year. The Hebrew calendar is adjusted with the solar calendar in such a way that 15 Nisan always coincides with a Sunday, Tuesday, Thursday, or Saturday.