Easter Sunday changes every year.

Easter Sunday is the Sunday following the Paschal Full Moon (PFM) date for the year.

In June 325 A.D. astronomers approximated astronomical full moon dates for the Christian church, calling them Ecclesiastical Full Moon (EFM) dates.

From 326 A.D. the PFM date has always been the EFM date after March 20 (which was the equinox date in 325 A.D.).

1753 was the first year Britain and its colonies used both the Gregorian calendar and the revised calculation for Easter.