I tried looking up the method of calculating the date of Easter, but the only thing any site really said was the Sunday after the first full moon after the vernal equinox. That in my mind is not really a calculation. I remember some years back seeing a method that involved dividing the year by 19 and applying the remainder to a table with a date corresponding to each possible remainder from 0 to 18. That date was defined as the Paschal full moon. Easter would then be the first Sunday after that date. It was noted that the Paschal full moon did not necessarily correspond to the astronomical full moon.
Is anyone familiar with this method? Can you link me to a site that explains it?
The 19 year cycle derives from the metonic cycle and comes from trying to make a calendar (e.g. the Hebrew calendar) where months are exactly lunar months (i.e. new moon to new moon) but doesn’t drift too far from the solar year. To do this 7 years out of these 19 have 13 months while the rest have 12.
The date of passover was the 15th day (which in a lunar month is always nearly a full moon) of the first month under this calendar so loosely the point of this calculation is trying to find out when passover would be under this calendar (without directly referencing it). Because of the “leap months” the mapping from that calendar to the Gregorian calendar varies over the 19 year cycle, hence the lookup table.
(Many more details in the video – including the fact that the “ecclesiastical equinox” is 21 March, no matter where those pesky astronomical bodies happen to lie at the time).
Somehow the mention of “ecclesiastical equinox” suddenly had me mentally singing the “Every sperm is sacred” song from Monty Python. Every Sperm is Sacred - Monty Python’s The Meaning of Life - YouTube. Logic. Ancient Religion. They fit together just oh so well. Just like peanut butter and anchovies.
The subject is discussed in detail the book Puzzles and Paradoxes by T. H. O’Beirne. He also gives a way to calculate the date directly that extends and corrects errors in existing algorithms. I got this to work in a spreadsheet. He also gives a slight modification to determine the date of the Paschal Full Moon, but I couldn’t get that to work.
He mentions that there can be a full Moon on Easter Sunday which is visible in some locations. “There may even be an eclipse to prove that the moon is full on Easter Sunday, as in Europe in 1903.”
The main thing I don’t get is that the “correct” date of Easter is clearly “whatever calculation the religious sect you belong to uses” no matter what weird conventions and lookup tables it uses, and any other calculation is at best coincidentally identical. It’s not like the Pope is going to tell Gauss, “well, you’ve proved me wrong, let’s have all the masses on your date instead”.
(The secondary thing I don’t get, is that if Easter meant to be the anniversary of the resurrection, why not just find out the date on the backwards-extended Gregorian calendar when it happened and make that the date every year like we do for other “anniversary of a thing” situations?)
The first day of the month based on sighting the new moon was observational. (It still is in some Islamic places.) Who knows what date the new moon for that Nisan was spotted on.
Some sects like Essenes used a slightly different calendar and therefore had Passover on a different date compared to others. Given the possible connection of Jesus’s group and Essenes we can’t really say which day Passover might have been observed by that particular sect of proto-Christians.
John suggests that the crucifiction was a day earlier. People try to wiggle around this but their arguments do not seem well founded other than an attempt to line things up that can’t be lined up…
To sum up, the Julian calendar (instituted by Julius Caesar) was pretty good, but not quite perfect, so it gradually fell out of synch with the natural year. A pope named Gregory recognized this, and tweaked the calendar so it’d stay in synch better, and to also fix all of the accumulated discrepancy. Since he was the Pope, all of the Catholic countries adopted his fix. And also since he was the Pope, all of the non-Catholic countries refused to go along.
That is just about the pithiest explanation of the History of Humanity that I have ever read. Bravo Good Sir. It applies not only to narrow situations involving Romans and calendars, but nearly everything else.
“F*** you and the horse you rode in on, even if you do have a better idea” seems to be the motive force and guiding star of damn near everything Humanity writ large has ever done or will ever do.
According to this video, there’s another confounding factor.
Although the modern Hebrew calendar runs on a strict 19-year Metonic cycle, it didn’t always work like this. Until some time around the third to sixth centuries, leap months were not added based on a predetermined cycle; they were added essentially on an ad-hoc basis depending on certain criteria.The main one of these criteria was “is the barley ripe yet?”, which served as a pretty good approximate indicator of whether or not the spring equinox had passed. And since the entirety of the New Testament takes place before the third century, the date calculation would have originally been based on this system, not on the stricter Metonic one.
A co-worker at the time said his wife, an elementary school teacher, was really good at keeping track on large numbers of children. When they went to see the movie, she said she was sure she counted about 80 different children in that musical number.
To the extent that the date of Easter is based on the Jewish calendar, my best advice is to do as the Jews do and Google “What date is Easter this year?”. It’s too complicated for anyone but an OCD rabbi to try to work out on their own.
I wish I had seen this thread at the time, one of the few questions I am well equipped to answer.
I am a practicing Eastern Orthodox Christian, and in our church the date of Pascha and the calculation is theologically important in a way that often is not as prominent in Western Christianity. The calendar itself is also important to Orthodox Christians and is a not small source of disagreements and strife in our Church and between our Church and Western Christians.
While I will give my best explanation here, I cannot speak better than the spiritual Fathers who have put out several great articles on this topic:
The data of Pascha is not based on the calculation for when Passover will occur and is not based on the Jewish calendar. This is not by accident but by design. One of the Nicene criteria for calculating Pascha was that they had to find a way to calculate it independent of the Jewish calendar. They had various reasons for this.
“Western Churches use Gregorian, Eastern Churches use Julian calendar” also is not a full explanation. The important additional difference is we input different dates for when the vernal equinox is and for when the full moon is. The Eastern and Western formula do use different calendars, and they also use different inputs, and this is why they are different dates.
There is actually significant debate, although lesser now than in the 1910s/20s (and some eras long ago–most debates in Orthodox recur every few generations) as to whether the Eastern Churches should retain the traditional calculations. You see, all Orthodox who have studied this know the simple reality–early Church Fathers built out calculation tables for the dates of future Paschas, and we have bound our Church to that ever since. It has been known for over 1000 years that these date calculations were not in sync with the actual astronomical events they were based on.
The most traditional view is that the tables are the tables, they are what the early Church Fathers made and agreed upon as a collective and the collective agreement of church leaders is supremely important to Orthodox Christians, which is why bishops who could not behave in this way like the one in Rome is schismatic from us now. The modernist view is the old tables are a math mistake, and you could correct the calculation to follow the real astronomical events. For a number of political and some theological reasons, no mainstream Orthodox Churches have adopted that modernist view (at least not for the movable feasts!), but it has at times been an area of real discussion.
As a little additional comment–not all Orthodox Churches use the Julian Calendar. Some use what is called the Revised Julian Calendar, which is in sync with the Gregorian calendar for the present and will not drift again until some date like 2700 or later. Because of the importance in Orthodoxy of maintaining communion with other Orthodox churches, the Churches that adopted Revised Julian (developed by a Serb, but rejected by Serbian Orthodox Church) adopt it for their Church calendar and for the fixed feasts, but not for the movable feasts. That is important because the most important feast (Pascha) is a movable feast, so an Orthodox Church that has adopted the Revised Julian calendar still uses all the old calculations for the movable feasts, so all Orthodox Christians celebrate Pascha on the same day. But we do not celebrate Christmas on the same day. Orthodox Churches that use Revised Julian celebrate Christmas on 25 December Revised Julian day, which is the same as 25 December Gregorian. Orthodox who still use original Julian for everything celebrate Christmas on January 7 Gregorian / Revised Julian. Christmas is a fixed feast, so will be 13 days apart in Revised vs original Julian.