Dates and Days

Easter calculator

When Easter falls, in any year, by either reckoning

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

Checked on every build against a published table of Western and Orthodox Easter dates. How it is checked

Enter a year to get Easter Sunday in the Western or Orthodox reckoning, or both, along with every feast that is defined as an offset from it. Easter is defined by arithmetic on fixed tables, so it is the one date on this site that can be computed with certainty.

The rule, and why it needs no 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. The "ecclesiastical full moon" is read from a fixed lunar table adopted centuries ago, whatever the Moon itself is doing, and 21 March is a fixed date standing in for the equinox, which drifts by a day or so either side of it. So Easter can be computed exactly, with integer arithmetic and no ephemeris, and it is the only date on this site with no tolerance attached to it.

Easter is not the only festival fixed by rule. The Hebrew calendar replaced sighting the new moon with arithmetic in the fourth century, and Passover, which the paschal full moon in Easter's own definition is reaching for, is computed the same exact way. The algorithm used here is the one usually credited to Butcher and set out in Meeus. On every build, the site's tests check both reckonings against a published table of Easter dates.

Why there are two answers

Most Orthodox churches still compute Easter on the Julian calendar, and that calendar now trails the Gregorian one by thirteen days. It is the calendar most of Europe gave up between 1582 and 1923, and its switch dates and skipped days are listed on another page here. The Orthodox date differs in most years, sometimes a week later and sometimes five. In 2025 the two fell on the same day, and in 2028 they do so again.

The thirteen-day gap is temporary. A calculator with 13 written into it goes wrong after 2099, so this page computes the shift from the year, and with the Orthodox or both reckonings selected, the line under the answer states the gap it used.

What hangs off the date

A large part of the Western church year is dated by counting from Easter. 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 follows a lunar cycle, and lunar months do not divide evenly into the calendar year. The rule ties Easter to 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 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 has the same shape (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 coincide again in 2028.
Will the thirteen-day difference always be thirteen days?
No. 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. This page works the gap out from the year you enter, so Orthodox dates from 2100 onward use the larger figure.
Is Easter ever on the same date two years running?
No. Across the years this page accepts, 1583 to 9999, Easter never falls on the same date two years running, in either reckoning. The date depends on a lunar cycle of roughly nineteen years interacting with the seven-day week, so the full pattern repeats only over very long periods. To compare two years, put each into the box above; the answer is exact.
How far back and forward does this work?
The page accepts any year from 1583 to 9999, in both reckonings. The Gregorian reckoning begins with the calendar reform of 1582; before that the Julian reckoning was the only one there was, so earlier years are refused. Everything here is integer arithmetic, so there is no accumulating error at either end.