Finding Easter
As an Astronomist I am often asked “How do they calculate the date of Easter?”, so here goes.
The simple answer is that Easter Sunday is on the first Sunday after the first full Moon on or after the Vernal equinox. The Vernal Equinox took place this year on March 20th and the first full moon after that was on April 2nd.
I say “simple” answer above because it isn’t quite how the date of Easter is reckoned for purposes of the liturgical calendar.
For a start, the ecclesiastical calculation of the date for Easter – the computus – assumes that the Vernal Equinox is always on March 21st, while in reality these days it is more frequently 20th March, like this year.
On top of that there’s the issue of what reference time and date to use. The equinox is a precisely timed astronomical event but it occurs at different times and possibly on different days in different time zones. Likewise the full Moon. In the ecclesiastical calculation the “full moon” does not currently correspond directly to any astronomical event, but is instead the 14th day of a lunar month, as determined from tables (see below). It may differ from the date of the actual full moon by up to two days.
There have been years (1974, for example) where the official date of Easter does not coincide with the date determined by the simple rule given above. The actual rule is a complicated business involving Golden Numbers and Metonic cycles and whatnot.
Here is an excerpt from the Book of Common Prayer that shows Anglicans how to determine the date of Easter for any year up to 2199:
The calculations are based on the approximately 19-year metonic cycle, which is why the above table will not work indefinitely
For this year we find that (2026+1=2027) ÷19=106 with a remainder of 13 (106 × 19 being 2014). The Golden Number for this year is therefore 13, or XIII in the Table. This gives the date of the Paschal Full Moon, which occured this year on 2nd April, which is indeed the day in the centre column next to XIII in the left-hand column in the table. The Sunday Letter is determined by the remainder of (2026+506+6)÷7, which is 4, so this year’s Sunday Letter is D. The date of Easter Sunday is given by the entry in the centre column next to the first occurrence of D in the right-hand column after the Golden Number XIII appears in the left-hand column, i.e. April 5th. I hope this clarifies the situation.
In the Dark 
April 3, 2026 at 10:31 pm
And that’s just in Western Europe and its spiritual descendants. The Eastern Orthodox churches have a different timing.
The question of when in the spring to celebrate Easter was an important issue at the Synod of Whitby in AD664. The decision of the indigenous celtic church, which the Romans had founded and which outlasted their departure, to accept the date of Easter proposed by the mission sent originally by Pope Gregory, meant that the celtic church accepted the Roman church’s authority. Colossians 2:16 is explicit that dates don’t matter, but whether or not to obey the papacy in the Saeculum Obscurum into which the papacy fell in the next centuries (also known as the pornocracy, from which you can draw your own conclusions) most certainly did matter.
April 3, 2026 at 10:42 pm
I heard from a colleague in Bulgaria that their Easter is not for another 2 weeks.
My understanding is that the Greek πόρνος primarily meant a (male) prostitute but also had a wider meaning applied to fornication generally or anyone who works only for money and for no other purpose.
April 3, 2026 at 9:59 pm
I thought that porne meant a (female) prostitute. But you can find what the papacy fell to by looking at details of the Saeculum Obscurum.
In the century and a half from 880AD there were some 35 popes, an average of less than five years each because many were deposed or murdered, often by persons acting on behalf of their successors. Nine months after Pope Formosus died in 896, his body was exhumed by a rival who had become the next Pope but one, Stephen. He verbally humiliated the corpse, putting it on trial and interrogating it. Seven popes came from the family of the Counts of Tusculum; the papacy was dominated by its matriarchs, Theodora and her daughters Marozia and Theodora. They made, or arranged the murder of, or slept with, or begat multiple popes. Marozia’s son became John XI in dubious circumstances. Her grandson was John XII (955-964); the English-language Catholic Encyclopaedia published in the early 20th century states that the Lateran palace of the popes under John XII essentially acted as a brothel. John double-crossed the Germanic king Otto the Great; Otto had deposed him after John had been accused (plausibly) at a synod of sacrilege, simony, perjury, murder, adultery and incest. John excommunicated those involved in the synod and, returning to Rome while Otto was campaigning, oversaw the murder or mutilation of the ringleaders. He died before Otto could deal with him, but Otto made sure the papacy was subordinate to the Emperor.
After Otto died in 973, one of the Roman factions had Pope Benedict VI, who had been protected by Otto, strangled. The papacy was taken by Boniface VII (not now ‘officially’ counted as a pope), but within two months a representative of Otto’s successor took the city of Rome by force. Boniface, pausing only to loot the Vatican treasury, fled to Constantinople. Whenever Imperial forces waned, he used force to try to seize the papacy, attempting to depose both Benedict VII and John XIV. Otto III oversaw the appointment as Pope (Sylvester II, 999-1003) of Gerbert, the first French pope and a scholar and a man of morals. But matters soon reverted; Benedict IX (elected 1032) lived a life of such debauchery that Pope Victor III, decades later, spoke of “his rapes, murders and other unspeakable acts. His life as a pope was so vile, so foul, so execrable, that I shudder to think of it.”[1] The same Catholic Encyclopaedia described him as a “disgrace to the Chair of Peter.” In 1044 a rebellion against him in Rome installed one Sylvester III, but Benedict’s political allies regained the papacy for him. Sylvester survived and insisted that he remained pope, however. Benedict then sold the papacy to a man who took the name Gregory VI, but Benedict soon changed his mind; Gregory then insisted that he was pope. So, when the (Germanic) Holy Roman Emperor Henry III planned his coronation in Rome in 1046, three claimants to the papacy were vying to crown him. He called a synod at Sutri (outside Rome) that sacked all three, and installed a German bishop as Pope, Clement II. Clement died after less than a year and Benedict IX made a further comeback.
[1] Dialogues, bk. III.
April 4, 2026 at 11:24 am
By the way, Otto the Great’s father was King Henry ‘the Fowler’, of Lohengrin fame.
April 4, 2026 at 3:26 am
As implemented by Dionysius Exiguus in 525 C.E., the date of Easter is based on the presumption that the vernal equinox is always March 21 and on ecclesiastical approximations to the lunar phases called epacts. This is the system still in use by the Orthodox churches. The Gregorian reform of 1582 c.e. included a more accurate approximation to the lunar phases for the calculation of Easter developed by Clavius and based on the suggestions of Naples astronomer Aloysius Lilius, and this is the system currently used by the Western churches. In 1997 the World Council of Churches proposed a unified system, Astronomical Easter, based on the first Sunday in Jerusalem after the first true full moon after the true vernal equinox. I believe this sytem is still under consideration, it being early days by ecclesiastical standards. Full details of all calculations, and many others, along with Lisp implementations, are contained in the splendid book “Calendrical Calculations” by Edward M. Reingold and Nachum Dershowitz, from which much of the above is taken
April 4, 2026 at 11:33 am
That sounds an interesting read. There is also Roger Beckwith’s book Calendar and Chronology, Jewish and Christian (2001).
April 5, 2026 at 3:25 pm
@telescoper.blog Clear as it ever was then.
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April 5, 2026 at 10:20 pm
@telescoper.blog
It was proposed to change it to the Sunday following the second Saturday in April. Never got through though.
https://en.wikipedia.org/wiki/Easter_Act_1928?wprov=sfla1
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April 7, 2026 at 11:30 pm
@telescoper.blog Just a test comment!
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