How easter date calculator works
Easter is a movable feast: the first Sunday after the first ecclesiastical full moon on or after March 21. Working that out for any year is the classical computus, and this calculator implements it in its standard integer form — the Anonymous Gregorian algorithm (Meeus/Jones/Butcher). No moon tables, no look-ups: a dozen divisions and remainders turn the year into a month and day, valid for every Gregorian year from 1583 to 4099.
Orthodox churches still date Easter by the Julian calendar, so the tool also runs Meeus' Julian-calendar computus and converts the result to a Gregorian date with the standard century correction. That conversion is why Orthodox Easter usually falls a week or more after the Western date — and occasionally, like in 2025, both land on the same Sunday.
From the Western Easter the calculator derives the other movable feasts of the liturgical year by fixed offsets: Ash Wednesday 46 days before, Palm Sunday 7 days before, Good Friday 2 days before, Easter Monday the day after, Ascension 39 days after and Pentecost 49 days after. It also shows both Easters for the following four years so you can plan ahead at a glance.