Vernal Equinox and Easter Sunday

Dear Tom,
Easter is always the Sunday following the first full moon after the spring Equinox. This year the equinox and full moon both occur on March 20 with the equinox four hours before the full moon. So why isn’t Easter on March 24?
— T. Owen, Roselle, Don Evans, Barrington
Pat Hussey, Norridge
Dear T., Don and Pat,
Technically it should be. The vernal equinox occurred March 20 at 4:58 CDT and was followed by the full moon at 8:43 p.m., so according to the rules, Easter would fall on March 24. However, since the equinox varies between March 19 and 21, it was decided by ecclesiastical rules to always use March 21 for the purpose of determining the date of Easter. Using the March 21 date for the equinox, the first full moon to follow occurs on April 19, so this year Easter will be celebrated on the following Sunday, April 21.

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