Easter Calculator — Date Finder

Easter is the Christian calendar’s most movable feast — it can fall on any Sunday between March 22 and April 25, and computing which one is a problem that occupied astronomers and computists for a thousand years. This calculator runs the classical solution, the Gregorian computus: enter any year and it returns Easter Sunday, with the season’s companion dates — Ash Wednesday, Good Friday, Ascension and Pentecost — derived from it by their fixed offsets.

The Rule: A Moon, A Sunday, A Boundary in March

The Council of Nicaea (325 AD) fixed the rule that still governs: Easter is the first Sunday after the first ecclesiastical full moon falling on or after March 21 — the church’s fixed date for the spring equinox. Two clocks must therefore be reconciled, the moon’s and the week’s, and the reconciliation is the computus. Note the careful word ecclesiastical: the full moon of the rule is not the astronomical moon but a tabulated one, cycling through a 19-year pattern (the Metonic cycle, in which lunar phases repeat on the same calendar dates to within a couple of hours), corrected by the Gregorian reform’s solar and lunar equations. That is why Easter calculation is an integer algorithm rather than an astronomy lookup — the date is defined by the tables, and the tables are what this page’s dozen lines of arithmetic encode.

Worked Example: Easter 2026

The current era’s calendar, run through the algorithm: for 2026 the computus returns Sunday, April 5, 2026 — and the season unfolds around it: Ash Wednesday February 18, Palm Sunday March 29, Good Friday April 3, Ascension Day May 14, Pentecost May 24. Neighbouring years show the feast’s wander at a glance: 2025 fell on April 20, 2027 will fall on March 28. The extreme bounds frame the playground: the earliest possible Easter, March 22, last occurred in 1818 and will not return until 2285; the latest, April 25, occurred in 1943 and returns in 2038. A date that can roam five weeks across the spring is why no diary can print Easter from memory — and why the computus, once the crown jewel of applied mathematics, still earns a page of its own.

The Algorithm, In Words

The anonymous Gregorian algorithm this widget runs (published in 1876, standardised by Meeus) is a masterpiece of integer compression, and its variables have meanings worth one paragraph. The year’s position in the 19-year Metonic cycle (a) drives the moon’s age; the century terms (b through g) apply the Gregorian corrections — dropped leap days, and the lunar equation’s slow adjustment as the Metonic cycle drifts against the true moon; h emerges as the date-offset of the Paschal full moon; the weekday machinery (i, k, l) advances to the following Sunday; and m handles the rare epact edge cases that keep two exceptional full-moon dates honest. Every operation is integer division or remainder — no trigonometry, no tables — which is how a computation that once occupied cathedral schools now fits in a paragraph of JavaScript without losing a day in four millennia of range.

Western and Orthodox Easter

One rule, two calendars, two dates — often. The Orthodox churches compute Easter by the same Nicene rule but within the Julian calendar’s framework: the equinox is taken as March 21 Julian (April 3 in the modern Gregorian reckoning), and the Julian lunar tables run about five days behind the Gregorian moon by this era. The results coincide in some years and diverge by one, four or five weeks in others — 2025 was a coincidence year (both April 20), while 2026 separates them (Western April 5, Orthodox April 12). This calculator serves the Western computation and labels it as such; anyone planning around both traditions (travel, mixed families, Greek or Russian colleagues’ holidays) needs both dates stated, never an average of them.

April’s Dominance and the Long Cycle

Run the computus across centuries and a distribution emerges: Easter falls in April in roughly three years out of four, and the full Gregorian cycle — the period after which the entire pattern of dates repeats exactly — runs 5,700,000 years, a number that measures how thoroughly the solar, lunar and weekly cycles refuse to synchronise cheaply. Within a human lifetime the practical texture is simpler: clusters of mid-April Easters, the occasional March visitor (2027’s March 28, 2024’s March 31), and school and business calendars quietly re-derived every year from this one computation. The feast’s refusal to sit still is not a bug in the system; it is the system itself — a lunar anniversary kept inside a solar calendar, forever negotiating its terms with both.

The Wider Season: Every Date From One

Easter’s computation anchors a constellation of movable feasts that all hang off its date by fixed offsets — which is why the computus, and not any single holiday, is the real object of study. Septuagesima Sunday (−63 days) opens the pre-Lenten season; Mardi Gras, or Shrove Tuesday, is −47; Ash Wednesday −46; Palm Sunday −7; Maundy Thursday −3; Good Friday −2; Easter Monday +1; Ascension Day +39; Pentecost +49; Trinity Sunday +56; Corpus Christi +60 in the traditional reckoning (the Thursday after Trinity). A calendar with a dozen feasts has, computationally, a single moving part — compute Easter and the season assembles itself around it, as this page’s companion list demonstrates in miniature.

Fixing Easter: The Reform That Never Lands

Every generation proposes to end the computus — a fixed Sunday in April, or the astronomical rule computed honestly from the Jerusalem meridian (the 1997 Aleppo proposal of the World Council of Churches, the most serious modern attempt) — and every generation’s calendars continue to be computed by the old integer tables instead. The obstacles are ecumenical rather than mathematical: no church wishes to move first, and a feast defined by a seventeen-century-old rule carries its history as part of its meaning. The calculator takes no side; it notes only that the proposals would make pages like this one considerably shorter, and that seventeen centuries of computists would have been put out of their favourite and most honourable job.

Related Tools

More from the Other Calculators hub: the School Age Calculator — the calendar’s other annual riddle — and the Letters to Numbers Converter for the holiday’s puzzle hunts.

Frequently Asked Questions

When is Easter 2026?

Sunday, April 5, 2026 (Western/Gregorian reckoning), with Good Friday on April 3 and Easter Monday on April 6, in the middle of the feast’s most familiar territory. The calculator confirms it from the computus rather than a stored table — enter 2026 and the algorithm derives the date, the same derivation it performs for any year in its range, which is the difference between a calendar lookup and a calculator.

Why does Easter move every year?

Because it is chained to a lunar event (the first full moon on or after the fixed equinox date, March 21) and then to a weekday (the Sunday after). Lunar months run about 29.5 days against the solar calendar’s pattern, so the full moon’s date slides by roughly 11 days a year, and the wait for Sunday adds up to six more — compounded, a five-week range of possible dates, March 22 to April 25. Fixed feasts like Christmas sit still because they answer to the solar calendar alone.

What is the computus?

The body of algorithms for computing Easter — for a millennium the most demanding computation in ordinary life, taught in cathedral schools, tabulated by Bede, and reformed by the Gregorian calendar commission of 1582 (whose lunar corrections this page’s century terms encode). The algorithm here is the standard all-integer form: exact for the Western Easter for every year from 1583 forward, no astronomical observation required, because the feast is defined by the ecclesiastical moon, not the sky’s.

How is Ash Wednesday calculated?

By subtraction: Ash Wednesday opens Lent, 46 days before Easter Sunday (40 fast days plus the six Sundays, which are not fast days). From April 5, 2026, the subtraction lands on February 18, 2026 — the calculator prints it with the other companions, all derived by fixed offsets from the one computed date: Palm Sunday −7, Good Friday −2, Ascension +39, Pentecost (Whit Sunday) +49. The whole season is one computus and a handful of constants.

When do Western and Orthodox Easter coincide?

In roughly a third of years, by the interplay of the two lunar tables and the 13-day calendar offset in this era — 2025 (April 20 for both) was the most recent, and 2028 (April 16) will be another. In split years the Orthodox date is always the later, by one, four or five weeks. Ecumenical proposals to fix a common date recur and remain proposals; the two computations this creates are a fact of the calendar landscape, and this page’s job is to compute the Western one correctly and label it plainly.

What are the earliest and latest possible Easters?

March 22 and April 25, the rule’s geometric limits — the full moon cannot be ecclesiastically earlier than March 21 (so Sunday cannot precede the 22nd) nor the Sunday-chase later than April 25. Both extremes are rare guests: March 22 last came in 1818 and returns in 2285; April 25 came in 1943 and returns in 2038. Most years cluster in the middle distance (early-to-mid April is the clear statistical mode), a statistic the computus makes auditable across any span of years you care to test it on, one year at a time.