Why Easter Moves Every Year: The Moon Rule, the Computus and the Dates to 2038

Why the Moon at all: the Passover link

Easter commemorates events that happened around the Jewish Passover, which is itself a lunar festival: Passover begins on 15 Nisan, a date set by the Moon. The earliest Christians therefore celebrated Easter in spring, near Passover, but they disagreed about the exact day. Some churches kept Easter on the Passover date itself, whatever weekday it fell on. Others insisted it must always be a Sunday, the day of the Resurrection.

The Council of Nicaea in 325 settled the principle in favour of Sunday, and independent of the Jewish calendar: Easter would be the Sunday after the first full Moon after the spring equinox. That decision is why Easter is lunar but not Jewish-calendar lunar, and why it has its own calculation, the computus, rather than borrowing Passover’s date. The link to Passover survives in the season — Easter always falls in the weeks around it — but the date itself comes from the church’s own tables.

The Paschal Moon is not the Moon in the sky

The most common confusion about Easter is the belief that it follows the astronomical full Moon. It does not. The church uses an ecclesiastical Moon: a mathematical model of the lunar cycle, built on the 19-year Metonic cycle, in which the Moon’s phases repeat almost exactly every 19 years. Each year is assigned a golden number (its position in that cycle) and an epact (the Moon’s age on 1 January), and from those the tables give the Paschal full Moon — the fourteenth day of the Paschal Moon.

The model is good but not exact, and it is deliberately frozen: the tables do not update with better astronomy. Over centuries the ecclesiastical Moon drifts slowly from the real Moon, and in individual years the two can disagree by a day. When a Moon-phase app says the full Moon is on a Saturday and Easter falls the Sunday after next rather than the next day, the app is not wrong and the church is not wrong — they are following different Moons, and only the church’s Moon sets Easter.

The same frozen-table logic explains the fixed 21 March. The rule uses the ecclesiastical equinox, 21 March every year, not the astronomical equinox, which wanders between 19 and 21 March. Fixing both the equinox and the Moon to tables makes the computation stable and repeatable for centuries — at the price of occasional disagreement with the sky.

The computus, step by step

The computus is the algorithm that turns a year into an Easter date. In its classic Gregorian form it runs like this: from the year, compute the golden number (the year’s place in the 19-year cycle) and the century corrections (which adjust for the Gregorian calendar’s rule that century years are leap years only when divisible by 400). Those give the Paschal full Moon’s date, and the Sunday letter — which weekday each date falls on — gives the following Sunday.

Traced for 2027, the arithmetic gives a Paschal full Moon so early that Easter lands on 28 March, near the early end of the window. The intermediate values are a golden-number remainder of 13 and a lunar correction of 1, which together place the Paschal full Moon in the week before Easter, with the next Sunday on 28 March. For 2028 the same steps give a lunar correction of 20, placing the Paschal full Moon in mid-April and Easter on 16 April. The same short calculation produces every date in the table below, and it is the calculation this site’s Easter calculator runs.

You do not need to run it by hand — that is what the calculator is for — but knowing that it is a fixed algorithm, not an observation, explains two things: why Easter dates can be published centuries in advance, and why they never change when astronomy improves. The tables are the authority, and they were set centuries ago.

The whole season moves

Easter is the centre of a season, and every date in that season is counted from it. 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. For 2027 that gives Ash Wednesday on 10 February, Palm Sunday on 21 March, Good Friday on 26 March, Easter Monday on 29 March, Ascension on 6 May and Pentecost on 16 May. For 2028, an April Easter, the season shifts with it: Ash Wednesday on 1 March, Palm Sunday on 9 April, Good Friday on 14 April, Easter Monday on 17 April, Ascension on 25 May and Pentecost on 4 June.

The practical lesson is to plan the season, not the day. A school term, a holiday or a wedding planned around “Easter” needs the whole set of dates, because Lent, Holy Week and Pentecost all move by exactly the same number of days as Easter Sunday itself.

Why the East celebrates on a different Sunday

Western churches use the Gregorian calendar, adopted in 1582. Orthodox churches still compute Easter on the Julian calendar, which runs 13 days behind the Gregorian calendar in the 20th and 21st centuries. The two computations therefore usually land on different Sundays — sometimes a week apart, sometimes five weeks apart, as in 2027, when Western Easter is 28 March and Orthodox Easter is 2 May, or 2035, when the gap is 25 March against 29 April.

Occasionally they coincide, and the coming years have several coincidences: 2028 (both 16 April), 2031 (both 13 April), 2034 (both 9 April), 2037 (both 5 April) and 2038 (both 25 April, the latest possible date). The coincidence happens when the Julian and Gregorian computations, despite different calendars, land on the same Sunday. The Orthodox date shown here is converted to the Gregorian calendar — the date on a wall calendar — after shifting the Julian result by the century offset.

The two Easters have been a standing ecumenical question for a century, and the difference is calendrical, not theological: both churches apply the same Nicaean principle, to different calendars. Any future common date would come from agreeing on one calendar or one computation, not from changing the principle.

Easter dates from 2026 to 2038

The table below gives Western and Orthodox Easter Sundays for the next thirteen years, computed by the two methods described above and verified against published Easter tables. Three patterns are worth noticing. First, the Western date swings across the whole window in just a few years: 28 March in 2027 and 2032, 25 April in 2038. Second, coincidences cluster: five of the thirteen years have both Easters on the same day. Third, the widest gaps come in early-Western years, when the Julian computation has not yet caught up: 2027 and 2035 both have five-week gaps.

2026: Western 5 April, Orthodox 12 April. 2027: Western 28 March, Orthodox 2 May. 2028: both 16 April. 2029: Western 1 April, Orthodox 8 April. 2030: Western 21 April, Orthodox 28 April. 2031: both 13 April. 2032: Western 28 March, Orthodox 2 May. 2033: Western 17 April, Orthodox 24 April. 2034: both 9 April. 2035: Western 25 March, Orthodox 29 April. 2036: Western 13 April, Orthodox 20 April. 2037: both 5 April. 2038: both 25 April.

Beyond 2038, the extremes of the whole system are 22 March at the early end — last in 1818, next in 2285 — and 25 April at the late end, which 2038 itself reaches. No Easter in any year, past or future under this rule, falls outside 22 March to 25 April.

The campaigns for a fixed Easter

The movable date has annoyed planners for as long as there have been planners. The most serious attempt in English law is the Easter Act 1928, which would fix Easter to the Sunday after the second Saturday in April — but only when an Order in Council brings it into force, which has never happened, because the Act was written to wait for international agreement that never came.

The churches have discussed a common date repeatedly. A 1997 consultation in Aleppo proposed that all churches use the astronomical full Moon and the astronomical equinox, calculated for the meridian of Jerusalem, which would keep the Nicaean principle but replace the tables with observation. It was not adopted, and the tables remain the authority. The practical result is that Easter will keep moving for the foreseeable future, and the calculator, not the calendar, is the tool for it.

Planning around a movable Easter

Three habits make a movable Easter easy. First, look up the year, not the season: “Easter is in April” is wrong in 2027, 2032 and 2035, when it falls in late March. Second, take the whole season at once — Ash Wednesday through Pentecost — because every date in it moves together, and a plan that fixes only Easter Sunday will misplace Lent and Pentecost. Third, check holiday status separately: Good Friday and Easter Monday are holidays in many countries but not all, and the list changes by jurisdiction, so the date and the day off are two different questions.

For a single year, the fastest route is the Easter calculator on this site: one year in, Easter Sunday, the Orthodox date, all ten movable feasts and the nearby years out. For the longer view, the 2026–2038 table above covers every plan most people will make.