Easter Date Calculator
Find the date of Easter Sunday for any year using the computus algorithm. Enter values for instant results with step-by-step formulas.
Formula
Computus (Anonymous Gregorian Algorithm)
The computus uses the Metonic cycle (19-year lunar cycle), century corrections, and modular arithmetic to find the date of the paschal full moon. Easter Sunday is the first Sunday following this paschal full moon on or after March 21.
Worked Examples
Example 1: Finding Easter 2025
Problem: What date is Easter Sunday in 2025?
Solution: Using the computus algorithm for year 2025:\na = 2025 mod 19 = 11\nb = floor(2025/100) = 20, c = 2025 mod 100 = 25\nd = floor(20/4) = 5, e = 20 mod 4 = 0\nf = floor((20+8)/25) = 1, g = floor((20-1+1)/3) = 6\nh = (19*11+20-5-6+15) mod 30 = 28\ni = floor(25/4) = 6, k = 25 mod 4 = 1\nl = (32+0+12-28-1) mod 7 = 1\nm = floor((11+308+22)/451) = 0\nmonth = floor((28+1-0+114)/31) = 4 (April)\nday = (28+1-0+114) mod 31 + 1 = 20
Result: Easter Sunday 2025 falls on April 20, 2025
Example 2: Related Holy Days for 2024
Problem: What are the key dates related to Easter in 2024?
Solution: Easter 2024 = March 31, 2024\nAsh Wednesday = March 31 - 46 days = February 14\nPalm Sunday = March 31 - 7 days = March 24\nGood Friday = March 31 - 2 days = March 29\nAscension = March 31 + 39 days = May 9\nPentecost = March 31 + 49 days = May 19
Result: Ash Wednesday: Feb 14 | Palm Sunday: Mar 24 | Good Friday: Mar 29 | Easter: Mar 31 | Ascension: May 9 | Pentecost: May 19
Frequently Asked Questions
How is the date of Easter calculated each year?
Easter is calculated using the computus algorithm, a set of mathematical rules established by the Council of Nicaea in 325 AD and later refined. The rule states that Easter falls on the first Sunday after the first full moon occurring on or after the March equinox (fixed as March 21). The algorithm uses modular arithmetic to determine the golden number (position in the 19-year Metonic cycle), the century-based corrections, and the exact date of the paschal full moon. This calculation produces Easter dates that can range from March 22 at the earliest to April 25 at the latest in the Gregorian calendar.
Why does Easter fall on a different date every year?
Easter is a moveable feast because its date depends on both the solar calendar (the March equinox) and the lunar calendar (the first full moon after the equinox). Since the lunar cycle is approximately 29.5 days, it does not align neatly with the 365-day solar year. The combination of these two astronomical cycles creates a pattern where Easter shifts around within a 35-day window from March 22 to April 25. This lunisolar calculation method was inherited from the Jewish calendar, as the original Easter was linked to Passover, which itself follows the Hebrew lunisolar calendar system.
What is the difference between Western and Orthodox Easter?
Western Easter (Catholic and Protestant) uses the Gregorian calendar adopted in 1582, while Orthodox Easter uses the older Julian calendar for its calculations. The Julian calendar is currently 13 days behind the Gregorian calendar, so the March equinox and paschal full moon fall on different dates in the two systems. Sometimes both Easters coincide, but more often Orthodox Easter falls one, four, or five weeks after Western Easter. Easter Date Calculator computes the Western (Gregorian) Easter date. The two traditions have discussed calendar unification multiple times but have not yet reached agreement on a shared calculation method.
What are the related holidays that depend on Easter?
Many Christian holidays are calculated relative to Easter Sunday. Ash Wednesday falls 46 days before Easter and marks the beginning of Lent. Palm Sunday is one week before Easter. Maundy Thursday commemorates the Last Supper three days before Easter. Good Friday is two days before Easter. Holy Saturday is the day before. Easter Monday is the day after, and it is a public holiday in many countries. Ascension Day falls 39 days after Easter, and Pentecost occurs 49 days after Easter. All of these dates shift each year because they are all anchored to the moveable Easter date.
What is the Metonic cycle and how does it relate to Easter?
The Metonic cycle is a period of approximately 19 years after which the phases of the moon recur on the same dates of the solar calendar. It was discovered by the Greek astronomer Meton of Athens in 432 BCE. The computus algorithm uses the golden number, which is the position of a given year within the current Metonic cycle, calculated as (year mod 19) + 1. This golden number determines the date of the paschal full moon. Because the lunar cycle repeats every 19 years, Easter dates also follow a repeating pattern, though Gregorian calendar corrections for century years introduce slight variations over longer timescales.
What are the earliest and latest possible dates for Easter?
The earliest possible Easter date is March 22, and the latest is April 25 in the Gregorian calendar. March 22 Easter is extremely rare, occurring only when the paschal full moon falls on March 21 (the equinox itself) and that date happens to be a Saturday, making the following Sunday March 22. The last March 22 Easter was in 1818 and the next will not occur until 2285. An April 25 Easter is also rare, last occurring in 1943 and next in 2038. The most common Easter dates fall in early to mid-April, with April 19 being statistically the most frequent Easter date over long periods.