What is on the first Sunday after the first full moon after March 21st?
Yep, it’s Easter, more or less. “The usual statement, that Easter Day is the first Sunday after the full moon that occurs next after the vernal equinox, is not a precise statement of the actual ecclesiastical rules. The full moon involved is not the astronomical Full Moon but an ecclesiastical moon (determined from tables) that keeps, more or less, in step with the astronomical Moon. The ecclesiastical rules are: Easter falls on the first Sunday following the first ecclesiastical full moon that occurs on or after the day of the vernal equinox; this particular ecclesiastical full moon is the 14th day of a tabular lunation (new moon); and the vernal equinox is fixed as March 21. resulting in that Easter can never occur before March 22 or later than April 25. The Gregorian dates for the ecclesiastical full moon come from the Gregorian tables. Therefore, the civil date of Easter depends upon which tables – Gregorian or pre-Gregorian – are used.
