Dates and Days

Easter calculator

When Easter falls, in any year, by either reckoning

Easter is the one date on this site that can be computed with certainty for any year at all — the definition is arithmetic, not astronomy. Both the Western and Orthodox reckonings are shown, along with every feast that is defined as an offset from it.

Easter Sunday— Good Friday— Ash Wednesday— Pentecost— Days from today—
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The movable feasts — every date defined as an offset from Easter
FeastDateOffset

The rule, and why it is arithmetic rather than astronomy

Easter is the first Sunday after the first ecclesiastical full moon falling on or after 21 March. Every term in that sentence is a definition rather than an observation. The "ecclesiastical full moon" comes from a fixed lunar table adopted centuries ago, not from where the Moon actually is; and 21 March is a fixed date, not the actual equinox, which drifts by a day or so either side. The consequence is convenient: Easter can be computed exactly, for any year, with integer arithmetic and no ephemeris. It is the only date on this site with no tolerance attached to it.

The algorithm used here is the one usually credited to Butcher and set out in Meeus. It is checked on every build against a published table of Easter dates rather than against itself, because an algorithm asserted against its own output merely pins whatever it did first.

Why there are two answers

Most Orthodox churches compute Easter by the older reckoning, on the Julian calendar, which now runs thirteen days behind the Gregorian one. That produces a different date in most years — sometimes a week later, sometimes five. The two coincide occasionally: they did in 2025, and they will again in 2028.

The thirteen-day gap is not permanent, and this page does not treat it as though it were. It becomes fourteen days in 2100 and fifteen in 2200, because the Gregorian reform dropped three leap days every four hundred years. A calculator with 13 written into it will be quietly wrong for everyone alive in 2100, which is a long way off and is still not a reason to hardcode it.

What hangs off the date

A large part of the Western church year is defined by counting from Easter rather than by any calendar date of its own. Ash Wednesday is forty-six days before — the forty days of Lent, plus the six Sundays, which are not counted as fast days. Good Friday is two days before, Ascension Day thirty-nine days after, Pentecost forty-nine. Shrove Tuesday, which is Mardi Gras, is the day before Ash Wednesday and therefore forty-seven days before Easter. Every one of them moves with Easter, which is why the whole cluster is called the movable feasts, and why a year with an early Easter has an early Carnival.

Questions

Why does Easter move around so much?
Because it is tied to a lunar cycle rather than to a calendar date, and the two do not divide evenly. Easter is the first Sunday after the first ecclesiastical full moon on or after 21 March, which places it anywhere from 22 March to 25 April in the Western reckoning — a window of thirty-five days. The whole window really is used: across the eight hundred years from 1600 to 2400 Easter falls on every one of those thirty-five dates at least once.
Why do you show a different date for Orthodox Easter?
Because most Orthodox churches use the older reckoning, computed on the Julian calendar, which currently runs thirteen days behind the Gregorian calendar in civil use. The underlying rule is the same idea — the first Sunday after a notional full moon following a fixed spring date — but it is applied to a different calendar with a different lunar table, so the answers usually differ. They coincided in 2025 and will again in 2028.
Will the thirteen-day difference always be thirteen days?
No, and this page does not assume it is. The gap grows by three days every four hundred years, because the Gregorian reform removed three leap days from each four centuries and the Julian calendar kept them. It becomes fourteen days in 2100 and fifteen in 2200. The shift is computed here from the year rather than written in as a constant, which is a small thing now and the difference between right and wrong for anyone using this after 2099.
Is Easter ever on the same date two years running?
It can happen, though not often. Because the date depends on a lunar cycle of roughly nineteen years interacting with the seven-day week, the pattern repeats only over very long periods and near-repeats are irregular. If you want to check a specific pair of years, put each into the box above; the answer is exact, so there is nothing to interpret.
How far back and forward does this work?
The Gregorian computation is valid for any year from 1583 onward, which is when the reformed calendar came into use; before that the Julian reckoning was the only one there was. The arithmetic itself will happily run on any year you give it, and for years before the reform the Western column is telling you what the modern rule would have produced rather than what anyone actually observed. Everything here is integer arithmetic, so there is no accumulating error at either end.