Easter Date Calculator

How the date of Easter is set

Easter is the first Sunday after the first full moon that falls on or after the spring equinox. That sentence is the rule almost everyone has heard, and it is close to right, but the full definition is a church rule rather than an astronomy problem.

The equinox in the rule is fixed at March 21, not the actual astronomical equinox, which can fall on March 19, 20 or 21 depending on the year and the time zone. The full moon is not the astronomical full moon either. It is the paschal full moon from a table of lunar dates the church adopted centuries ago, which can differ from the real full moon by a day or two.

The result is a date that moves every year inside a 35 day window, from March 22 to April 25 for Western churches. The calculation that produces it is called computus, and the version used with the Gregorian calendar is the one this page implements.

Easter is a Sunday by definition, so the date is always a Sunday. What changes is which Sunday, and the answer depends only on the year.

The rule in four steps

Stated as a procedure, the rule reads like this. First, find the first full moon on or after March 21 using the church's lunar table. Second, if that full moon falls on a Sunday, move to the following Sunday, because Easter must come after the full moon. Third, if the resulting Sunday is in March or April, that is Easter. Fourth, if the arithmetic pushes past April 25, the tables are built so it cannot.

The reason for the Sunday rule is that Easter is tied to the resurrection, which the Gospels place on the first day of the week. The reason for the full moon rule is the Jewish Passover, which is set by the lunar month of Nisan. The Council of Nicaea in 325 AD asked for a single date that all churches could agree on, and the rules have been refined since then.

Two constraints come out of this and surprise people. Easter can fall on March 22 only when the paschal full moon lands on March 21 and that day is a Saturday. Easter can fall on April 25 only when the paschal full moon lands on April 18 and that day is a Sunday. Both are rare, which is why the extremes are worth a table.

Why Easter moves between March 22 and April 25

The window is 35 days wide because the lunar month is about 29.5 days and the week is 7. The paschal full moon can land anywhere from March 21 to April 18, and the following Sunday can be up to 7 days later, which gives March 22 as the earliest possible date and April 25 as the latest.

In practice the dates cluster in April. The middle of the window, around April 8, is where the most Easters land over a long run of years, and the ends are rare. The extremes below are the years to quote when someone asks how early or late Easter can be.

A March 22 Easter will not happen again until 2285, so anyone reading this will see March 23 or later. The next April 25 Easter is 2038, which is close enough to plan around.

The spread matters for anything tied to the date: school spring breaks, retail seasons, the start of Lent, and the timing of spring weather in places where Easter is a travel weekend. Two consecutive years can differ by four weeks.

The algorithm behind the calculator

The calculation used here is the anonymous Gregorian computus, often called the Meeus/Jones/Butcher algorithm after the authors who popularised it. It uses integer arithmetic only, which is why it fits in a few lines of JavaScript and gives the same answer every time.

It works in three stages. The golden number stage finds where the year sits in the 19 year Metonic cycle of lunar phases. The epact stage turns that into the age of the moon on March 21. The weekday stage finds the next Sunday after the paschal full moon. The final lines convert the day count into a month and a day.

The U.S. Naval Observatory publishes the same algorithm on its Date of Easter page, with the note that all variables are integers and remainders are dropped. That integer detail is the part people get wrong when they reimplement it in a spreadsheet, because a floating point division gives a different answer at the rounding step.

The algorithm covers the Gregorian calendar from 1583 onward. For years before that, the Julian calendar and a different computus apply, and the results on this page are not meant for historical dates.

Worked example: Easter in 2026

Running the algorithm for 2026 shows how the pieces fit. Start with the year and the century: 2026 - 19 x 106 = 12, which is the golden number for the year. The century is 20 and the year inside the century is 26.

The epact step combines the century corrections with the golden number: 19 x 12 = 228, then 228 + 20 - 5 - 6 + 15 = 252. Taking 252 modulo 30 leaves 12, which is the epact, the notional age of the moon on March 21.

The weekday step: 32 + 0 + 12 - 12 - 2 = 30, and 30 - 28 = 2, so the correction is 2 days. Adding the epact and the correction to the March offset gives 12 + 2 + 114 = 128. Dividing 128 by 31 gives 4 with 4 left over, so the month is April and 128 - 124 = 4, which makes the day 4 + 1 = 5.

Easter 2026 is April 5, 2026. That is the 95th day of the year, 17 days before Earth Day on April 22, and 46 days after Ash Wednesday, which was February 18.

The Orthodox date for the same year is April 12, one week later, because the Julian computus lands on a different Sunday and then shifts by 13 days when converted to the Gregorian calendar.

Western and Orthodox Easter use different calendars

Most American calendars show the Western date, which is what Catholic and Protestant churches use. Orthodox churches in the US and around the world use the Julian calendar for the fixed feasts and a Julian-based computus for Easter, so their date often differs.

The Julian calendar runs 13 days behind the Gregorian for years from 1900 to 2099. An Orthodox Easter computed on the Julian calendar is therefore shifted forward by 13 days when it is written on a Gregorian calendar. The two dates coincide when the Julian date plus 13 lands on the same Sunday as the Western date, which happens in roughly one year in three.

The Orthodox window is April 4 to May 8 on the Gregorian calendar. The earliest case, April 4, last happened in 2010. The latest, May 8, last happened in 1983 and comes again in 2078.

If a family celebrates both, the gap can be zero, one week, or as much as five weeks. 2024 is the wide case: Western Easter was March 31 and Orthodox Easter was May 5, a gap of 35 days.

The dates that move with Easter

Lent and the weeks after Easter are all set by counting back or forward from Easter Sunday. The table gives the offsets, and the dates are the 2026 values so you can check the arithmetic against a calendar.

The 46 days before Easter are the 40 weekdays of Lent plus the six Sundays, which are not counted as fast days. That is why Lent feels longer than 40 days when you count it on a calendar.

Carnival, Mardi Gras and Shrove Tuesday all sit on the day before Ash Wednesday, so they move with the same 46 day offset. In 2026 Mardi Gras in New Orleans falls on February 17.

Easter dates through 2035

The table lists the Western and Orthodox dates for the next decade, computed with the algorithms described above. Orthodox dates are shown on the Gregorian calendar, which is how they appear on a US calendar.

The pattern of gaps repeats because both calendars are cyclic. The Western date repeats on a 5.7 million year cycle in theory, but the practical pattern over a human lifetime is the 19 year Metonic cycle plus the leap year corrections.

The Church of England publishes its own table of Easter and other variable dates for the years its lectionary covers, which is a useful cross-check if you want to confirm a date against an official church source.

Dates are for Western churches using the Gregorian calendar and for Orthodox churches using the Julian computus converted to Gregorian. Local observance and the definition of Easter used by a specific denomination can differ.