Why are Western and Orthodox Easter different?

Both use the same rule, but Orthodox churches still calculate the equinox and the ecclesiastical full moon on the Julian calendar. The Julian calendar drifts about 13 days behind the Gregorian, so the two dates can diverge by up to five weeks.

Is the algorithm accurate?

Yes — for the supported range (1583–4099) it matches every published Western Easter date. The Orthodox calculation matches published Eastern Easter dates to the day.

Why the lower bound of 1583?

The Gregorian calendar was introduced in October 1582. Before that, Western and Eastern churches both used the Julian calendar, so the Gregorian algorithm is not meaningful for earlier years.

What other holidays depend on Easter?

The tool shows Ash Wednesday, Palm Sunday, and Pentecost; you can derive others (Good Friday = Easter − 2, Ascension = Easter + 39, Trinity = Easter + 56) the same way.

Easter Date Calculator

Find Western and Orthodox Easter dates plus Ash Wednesday, Palm Sunday, and Pentecost.

Written by Golam Rabbani, Founder & Lead Engineer

This interactive tool requires JavaScript. Read the formula and worked example below; you can compute the result by hand.

How to use this easter date calculator

Enter a year between 1583 and 4099.
Press "Find Easter date".
Read Western Easter, Orthodox Easter (rendered on the Gregorian calendar), and the related dates (Ash Wednesday, Palm Sunday, Pentecost).
Use Copy to share the result or Reset to clear.

About this easter date calculator

Easter Sunday is the most movable feast in the Christian calendar: it is defined as the first Sunday after the first ecclesiastical full moon on or after 21 March (the vernal equinox). Because the actual date depends on a lunar-solar calculation, it varies by up to a month between years and differs between the Western (Gregorian) and Eastern Orthodox traditions, which still anchor the equinox to the Julian calendar.

This tool computes both. Western Easter uses the <strong>Anonymous Gregorian algorithm</strong> (often credited to Meeus, Jones, and Butcher), a closed-form integer formula that is exact for years 1583 through 4099. Orthodox Easter uses Meeus’s Julian-calendar algorithm and is then projected back into the Gregorian calendar via Julian Day Number arithmetic, so the displayed date is the Gregorian date your phone would show on the day. Three related dates — Ash Wednesday (Western Easter − 46), Palm Sunday (Western Easter − 7), and Pentecost (Western Easter + 49) — are derived from the Western Easter date.

Worked example: enter 2026. The tool reports Western Easter on Sunday 5 April 2026, Orthodox Easter on Sunday 12 April 2026, Ash Wednesday 18 February 2026, Palm Sunday 29 March 2026, and Pentecost 24 May 2026.

Useful for liturgical planning, school holiday scheduling, retail and travel forecasting, or simply settling the annual "when is Easter this year?" question.

FAQ

Why are Western and Orthodox Easter different?: Both use the same rule, but Orthodox churches still calculate the equinox and the ecclesiastical full moon on the Julian calendar. The Julian calendar drifts about 13 days behind the Gregorian, so the two dates can diverge by up to five weeks.
Is the algorithm accurate?: Yes — for the supported range (1583–4099) it matches every published Western Easter date. The Orthodox calculation matches published Eastern Easter dates to the day.
Why the lower bound of 1583?: The Gregorian calendar was introduced in October 1582. Before that, Western and Eastern churches both used the Julian calendar, so the Gregorian algorithm is not meaningful for earlier years.
What other holidays depend on Easter?: The tool shows Ash Wednesday, Palm Sunday, and Pentecost; you can derive others (Good Friday = Easter − 2, Ascension = Easter + 39, Trinity = Easter + 56) the same way.