How to use the easter date calculator
- Enter the year you want to check (1583 or later).
- Choose Western for Catholic and Protestant churches, or Orthodox for Eastern churches.
- Read the computed Easter Sunday date instantly.
- Review the related holy days: Ash Wednesday, Good Friday and Pentecost.
- Check the days until Easter row to see how far away it is from today.
How the Computus algorithm works
The date of Easter is not fixed on the calendar. It falls on the first Sunday after the Paschal full moon, which is the first ecclesiastical full moon on or after March 21. The Anonymous Gregorian algorithm, also called the Meeus/Jones/Butcher Computus, computes this without lookup tables.
For a given year Y, the algorithm calculates intermediate values using modular arithmetic. For example, for 2025:
- a = 2025 mod 19 = 11
- b = floor(2025 / 100) = 20
- c = 2025 mod 100 = 25
- d = floor(20 / 4) = 5
- e = 20 mod 4 = 0
- f = floor((20 + 8) / 25) = 1
- g = floor((20 - 1 + 1) / 3) = 6
- h = (19 * 11 + 20 - 5 - 6 + 15) mod 30 = 23
- i = floor(25 / 4) = 6
- k = 25 mod 4 = 1
- l = (32 + 2 * 0 + 2 * 6 - 23 - 1) mod 7 = 20 mod 7 = 6
- m = floor((11 + 11 * 23 + 22 * 6) / 451) = 0
- month = floor((23 + 6 - 7 * 0 + 114) / 31) = 4 (April)
- day = ((23 + 6 - 7 * 0 + 114) mod 31) + 1 = 20
This yields April 20, 2025 for Western Easter.
Western vs Orthodox Easter dates
Western churches use the Gregorian calendar and the Computus described above. Orthodox churches use the older Julian calendar rules to compute the Paschal full moon, then convert the result to the Gregorian calendar for civil use. Because the Julian calendar currently trails the Gregorian by 13 days, Orthodox Easter is the same day or later.
| Year | Western Easter | Orthodox Easter (Gregorian) |
|---|---|---|
| 2023 | April 9 | April 16 |
| 2024 | March 31 | May 5 |
| 2025 | April 20 | April 20 |
| 2026 | April 5 | April 12 |
| 2027 | March 28 | May 2 |
In some years, like 2025, both traditions coincide. In others they can be up to five weeks apart.
Days until Easter
The tool also functions as a quick reference for how many days remain until Easter. It compares the computed date against today's date in your local time zone. If that Easter has already passed, the row changes to days since Easter.
Knowing the days until Easter helps with planning school holidays, travel and church preparations. You can pair this with a date calculator if you need to add or subtract specific working periods around the holiday.
Historical background of the Computus
The word computus comes from Latin, meaning calculation. Determining the date of Easter was one of the most important mathematical problems in medieval Europe. The Council of Nicaea in 325 AD established the rule that Easter should fall on the Sunday following the first full moon after the vernal equinox.
Dionysius Exiguus created an early Easter table in 525 AD. When Pope Gregory XIII reformed the calendar in 1582, the algorithm was updated to correct the drift of the Julian calendar. The Meeus/Jones/Butcher method published in the 20th century distilled these rules into a compact set of integer operations suitable for computers. The Gregorian reform is why this calculator accepts years from 1583 onward.
Worked examples
| Example | Input | Result |
|---|---|---|
| Western Easter 2025 | Year: 2025; Tradition: western | Easter Sunday: April 20, 2025; Ash Wednesday: March 5, 2025; Good Friday: April 18, 2025; Pentecost: June 8, 2025; Ascension Day: May 29, 2025; Days since Easter: 563 |
| Orthodox Easter 2025 | Year: 2025; Tradition: orthodox | Easter Sunday (Julian): April 7, 2025; Easter Sunday (Gregorian): April 20, 2025; Good Friday: April 18, 2025; Pentecost: June 8, 2025; Ascension Day: May 29, 2025; Days since Easter: 563 |
| Western Easter 2024 | Year: 2024; Tradition: western | Easter Sunday: March 31, 2024; Ash Wednesday: February 14, 2024; Good Friday: March 29, 2024; Pentecost: May 19, 2024; Ascension Day: May 9, 2024; Days since Easter: 948 |
| Orthodox Easter 2024 | Year: 2024; Tradition: orthodox | Easter Sunday (Julian): April 22, 2024; Easter Sunday (Gregorian): May 5, 2024; Good Friday: May 3, 2024; Pentecost: June 23, 2024; Ascension Day: June 13, 2024; Days since Easter: 913 |
FAQ
When is Easter 2025?
Western Easter in 2025 falls on Sunday, April 20. Orthodox Easter also falls on April 20 in 2025, making it a rare year where both traditions share the same date.
Why does the date of Easter change every year?
Easter is tied to the lunar cycle rather than the solar calendar. It falls on the first Sunday after the Paschal full moon, which is the first ecclesiastical full moon on or after March 21. This causes the date to shift between March 22 and April 25.
What is the difference between Western and Orthodox Easter?
Western churches use the Gregorian calendar and a specific Computus algorithm. Orthodox churches calculate the Paschal full moon using the older Julian calendar rules, then convert the result to the Gregorian calendar. When the two dates differ, Orthodox Easter is one, four or five weeks later.
How many days before Easter is Ash Wednesday?
Ash Wednesday is exactly 46 days before Easter Sunday. It marks the beginning of Lent in Western Christianity, which consists of 40 fasting days plus six Sundays.
Can I use this easter date calculator for historical years?
Yes, but only for years 1583 and later. The Gregorian calendar was introduced in October 1582, so the algorithm used here is valid starting from 1583. For earlier years, the Julian calendar rules applied differently.
Is my data sent to a server when I use this tool?
No. The computation happens entirely in your browser using JavaScript. No year or date information is transmitted anywhere.
When is Pentecost relative to Easter?
Pentecost is always 49 days (seven weeks) after Easter Sunday. It commemorates the descent of the Holy Spirit upon the apostles.