How is the date of Easter calculated?

Easter is the first Sunday after the first ecclesiastical full moon on or after 21 March. This tool uses the Anonymous Gregorian (Meeus/Jones/Butcher) algorithm for Western Easter and the Meeus Julian-calendar algorithm for Orthodox Easter, converted to a Gregorian date.

Why do Western and Orthodox Easter differ?

The Orthodox church bases its computus on the older Julian calendar, while the Western church uses the Gregorian calendar. The two dates often differ by one to five weeks, and only occasionally coincide.

Does this send my input anywhere?

No. The whole calculation runs locally in your browser using arithmetic only — nothing is uploaded.

What is the earliest and latest Easter can fall?

For Western Easter the date ranges from 22 March to 25 April. Orthodox Easter, converted to the Gregorian calendar, falls between early April and early May and is never earlier than Western Easter.

What range of years does this calculator support?

It accepts any year from 1583 to 4099. 1583 is the first full year after the Gregorian calendar reform of 1582, so Western dates before then would be anachronistic.

Can Western and Orthodox Easter ever fall on the same day?

Yes. Because both depend on a full moon near the spring equinox, the dates occasionally coincide — for example in 2025 (20 April), 2028 and 2031.

Why is the Orthodox date computed on the Julian calendar?

The Eastern Orthodox church fixes the equinox and paschal full moon on the Julian calendar, then the result is shifted by 13 days to give a modern Gregorian date. That 13-day offset is what usually pushes Orthodox Easter later than Western Easter.

Easter Date Calculator

When is Easter? Find the date for any year

Easter Sunday is the most important movable feast in the Christian calendar, and its date shifts every year because it is tied to the moon rather than a fixed day. By the rule set at the First Council of Nicaea (325 AD), Easter falls on the first Sunday after the first ecclesiastical full moon on or after 21 March. The Western (Catholic and Protestant) churches compute it on the Gregorian calendar, while the Eastern Orthodox churches use the older Julian computus — so the two dates usually differ by one to five weeks.

How it works

This tool uses pure arithmetic — no lookup tables. For Western Easter it runs the Anonymous Gregorian algorithm (Meeus/Jones/Butcher): from the year it derives the golden number (year mod 19), the century, leap-cycle corrections, the epact and a weekday offset, then combines them into a month and day. For Orthodox Easter it runs Meeus’s Julian algorithm to get the Julian-calendar date, then adds a 13-day offset (valid for 1900–2099) to convert it to the Gregorian calendar. The weekday is read directly from a UTC date so the result always lands on a Sunday.

Example

Enter 2026 with the Western tradition and the algorithm returns April 5, 2026, a Sunday. Switch to Eastern Orthodox for the same year and you get April 12, 2026 — one week later, because the Julian computus places the paschal full moon differently.

Year	Western Easter	Orthodox Easter
2025	April 20	April 20 (same)
2026	April 5	April 12
2027	March 28	May 2

Everything is computed locally in your browser. No year or input ever leaves your device.