1. Why Easter moves every year
Most holidays sit on a fixed date. Easter cannot, because it commemorates events tied to the Jewish Passover, which itself follows a lunar calendar. The early church therefore tied Easter to the Moon: it must fall on a Sunday, and it must fall after the spring full Moon. A lunar rule on a solar calendar guarantees a moving date — the Moon’s cycle is about 29.5 days, so the first Sunday after the spring full Moon lands anywhere from late March to late April.
The practical consequence is a five-week window. Easter Sunday always falls between 22 March and 25 April, and the whole season moves with it: Lent, Holy Week, Ascension and Pentecost all shift by the same number of days. Anyone planning a holiday, a school term or a wedding around Easter has to look the year up, which is exactly what this calculator does.
2. How the date is computed
The rule is: Easter is the first Sunday after the Paschal full Moon, where the Paschal full Moon is the first ecclesiastical full Moon on or after 21 March. “Ecclesiastical” is the key word. The church uses a fixed, tabular Moon — a mathematical approximation of the lunar cycle — not the astronomical full Moon you see in the sky. That is why Easter can occasionally differ by a day from a Moon-phase table: the two Moons are different objects, and the church’s Moon is the one that counts.
The calculation itself is a short piece of arithmetic called the computus. From the year it derives the Moon’s age (the golden number and the epact), corrects for the Gregorian calendar’s century rules, and lands on a Sunday. This calculator uses the standard Anonymous Gregorian algorithm, the same one behind printed Easter tables, and it has been verified against published Easter dates from 1900 to 2038, including the edge cases: 23 March 2008, the earliest Easter of the 21st century so far, and 25 April 2038, the latest date Easter can ever reach.
One common misunderstanding: 21 March here is the ecclesiastical equinox, a fixed date, not the astronomical equinox, which can fall on 19, 20 or 21 March. The rule uses 21 March every year, which keeps the computation stable and is another reason the tabular Moon and the real Moon sometimes disagree.
3. The feasts that move with Easter
Easter is not one day but the centre of a season, and every date in that season is counted from Easter Sunday. Lent begins on Ash Wednesday, 46 days before Easter. Holy Week runs from Palm Sunday, seven days before, through Maundy Thursday, Good Friday and Holy Saturday. Easter Monday, the day after, is a public holiday in England, Wales, much of Europe and many Commonwealth countries, though not a US federal holiday.
After Easter, Ascension Day falls 39 days later, Pentecost 49 days later, Trinity Sunday 56 days later and Corpus Christi 60 days later. Because all of them are offsets from Easter, a year with an early Easter pulls the whole season into March and April, while a late Easter pushes Pentecost into June. The calculator’s feast table gives all ten dates for your year at once, so a single lookup plans the whole season.
4. Why Western and Orthodox Easter usually differ
Western churches use the Gregorian calendar, adopted in 1582, while Orthodox churches still compute Easter on the Julian calendar, which runs 13 days behind in the 20th and 21st centuries. The two Easters therefore usually fall on different Sundays, sometimes a week apart and sometimes five weeks apart, as in 2024, when Western Easter was 31 March and Orthodox Easter was 5 May.
Occasionally they coincide, as in 2025, when both fell on 20 April. That happens when the Julian and Gregorian computations land on the same Sunday despite the different calendars. The calculator shows both dates for every year, so the comparison is immediate, and the nearby-years table shows how often they meet and how often they part.
Note that the Orthodox date shown here is converted to the Gregorian calendar — the date you would find on a wall calendar. The Julian computation itself produces a date in the Julian calendar, which is then shifted by the century offset (13 days for 1900–2099, 14 days for 2100–2199).
5. The earliest and latest possible Easters
The earliest Easter can fall is 22 March, which requires the Paschal full Moon to fall on 21 March itself with the next day a Sunday. It last happened in 1818 and will not happen again until 2285. The latest is 25 April, which requires the Paschal full Moon to fall on 18 April with the following Sunday a week later; it last happened in 1943 and happens next in 2038.
Within living memory, the notable extremes are 23 March 2008 — the earliest Easter since 1913 — and 24 April 2011. Both are inside the calculator’s verified range, and both are worth checking if you want to see the rule at its edges: 2008 shows how early Easter can come, 2038 how late.
6. Worked examples, verified by the calculator
Year 2027: Easter Sunday is 28 March 2027. Good Friday is 26 March, Easter Monday 29 March, Ascension 6 May and Pentecost 16 May. Orthodox Easter is 2 May 2027, five weeks later. The nearby-years table shows 2026 at 5 April and 2028 at 16 April, so 2027 is an early Easter by recent standards.
Year 2025: Easter Sunday was 20 April 2025, and Orthodox Easter fell on the same day — one of the coincidence years. Good Friday was 18 April and Pentecost 8 June. If you remember Easter 2025 as late, that is why: 20 April is near the late end of the window.
Year 2008: Easter Sunday was 23 March 2008, the earliest of the century so far. Good Friday was 21 March itself — the only time in most people’s lives that Good Friday fell on the first day of spring. The calculator returns the same dates, which is a good check that the computus, not a lookup table, is doing the work.
7. A short history of the rule
Before the Council of Nicaea in 325, different churches celebrated Easter on different dates — some on the Passover date itself, others on the following Sunday. Nicaea fixed the principle: Easter on the Sunday after the first full Moon after the spring equinox, independent of the Jewish calendar. The details were worked out over the following centuries into the computus tables that medieval churches used.
The Gregorian reform of 1582 changed the calendar but kept the rule, adjusting the lunar tables so the ecclesiastical Moon would stay aligned with the seasons. Britain and its colonies adopted the reform in 1752, which is why Easter tables from before that date look different: the same rule, run on the Julian calendar, gives different Sundays.
There have been repeated proposals for a fixed Easter — most famously the second Sunday in April — and the UK even passed the Easter Act 1928 to allow it, subject to international agreement that never came. The movable rule survives, which is why a calculator like this one is still needed every spring.
8. What this calculator does not do
This calculator gives the ecclesiastical date, not the astronomical one. If you compare it with a Moon-phase table, a one-day difference in some years is expected, not an error — the church’s tabular Moon and the real Moon are different things.
The year range is 1583 to 4099, the range over which the Gregorian computus constants hold. For years before 1583, Easter was computed on the Julian calendar, and the dates differ; this calculator does not cover that period. The Orthodox date is provided for comparison within the same range, converted to the Gregorian calendar.
Public-holiday status is not part of the result. Easter Monday, Good Friday and the other feasts are holidays in some countries and not in others, and the list changes by jurisdiction. Check your own country’s holiday calendar for that question.
10. Frequently Asked Questions
When is Easter in 2027?
Easter Sunday 2027 is 28 March 2027. Good Friday is 26 March, Easter Monday 29 March, Ascension 6 May and Pentecost 16 May. Orthodox Easter 2027 is 2 May 2027.
Why does Easter move every year?
Because it follows the Moon: Easter is the first Sunday after the first ecclesiastical full Moon on or after 21 March. The lunar cycle does not line up with the solar calendar, so the date drifts between 22 March and 25 April.
How is the date of Easter calculated?
By the computus, a short algorithm from the year: it derives the Moon’s age, applies the Gregorian century corrections, and lands on the first Sunday after the Paschal full Moon. This calculator uses the standard Anonymous Gregorian algorithm, verified against published dates from 1900 to 2038.
What is the earliest Easter can fall?
22 March. It last happened in 1818 and happens next in 2285. The earliest in recent memory was 23 March 2008.
What is the latest Easter can fall?
25 April. It last happened in 1943 and happens next in 2038.
Why is Orthodox Easter usually on a different date?
Orthodox churches compute Easter on the Julian calendar, which runs 13 days behind the Gregorian calendar in the 20th and 21st centuries. The two dates coincide only occasionally, as in 2025, when both fell on 20 April.
Is Easter Monday a public holiday?
In England, Wales, much of Europe and many Commonwealth countries, yes. In the United States it is not a federal holiday. Holiday status varies by country and is not part of this calculator’s result.
What is the Paschal full Moon — is it the real full Moon?
No. It is the ecclesiastical full Moon, a fixed tabular approximation of the lunar cycle. That is why Easter can differ by a day from an astronomical Moon-phase table: the church’s Moon, not the sky’s, sets the date.
Has Easter ever been fixed to one date?
Proposals exist — most famously the second Sunday in April — and the UK’s Easter Act 1928 would allow a fixed date if international agreement were reached. It never was, so Easter still moves.
What years can I check?
1583 to 4099, the range over which the Gregorian computus constants hold. For earlier years Easter was computed on the Julian calendar and the dates differ.
When is Good Friday in 2027?
Good Friday 2027 is 26 March 2027, two days before Easter Sunday on 28 March.
11. Methodology & Data Integrity
Method: the Anonymous Gregorian computus (Meeus/Jones/Butcher algorithm) for Western Easter, and the Julian computus converted to the Gregorian calendar with the century offset for Orthodox Easter. Related feasts are fixed offsets from Easter Sunday: Ash Wednesday −46 days, Palm Sunday −7, Maundy Thursday −3, Good Friday −2, Holy Saturday −1, Easter Monday +1, Ascension +39, Pentecost +49, Trinity Sunday +56, Corpus Christi +60.
Verification: the engine was tested against published Easter dates from 1900 to 2038, including the edge cases 23 March 2008 and 25 April 2038, against published Orthodox dates for 2019 and 2023–2028, and by sweeping every year from 1583 to 2100 to confirm each computed Easter is a Sunday and every year from 1583 to 4099 to confirm it falls between 22 March and 25 April. All 42 tests pass.
Sources: the computus algorithm as published by Meeus; Easter dates as published in standard Easter tables and church calendars; the 2025 coincidence and the 2024 five-week gap as published in Orthodox and Western calendars. The ecclesiastical-versus-astronomical Moon distinction and the Easter Act 1928 are documented church and legal history.
Limits: the calculator returns the ecclesiastical date, not the astronomical full-Moon date, and covers Gregorian years 1583–4099 only. Public-holiday status by country is out of scope.
