YOUR HOST HAS Been volunteering in a Byzantine Catholic Parish that uses the Julian Paschalion and the Julian Calendar as well. Thus this week is Holy Week, with Pascha today, 16 April. In the US, for most Byzantine Catholics, last week was Holy Week so we’re really a Unicorn here. This has raised questions among parishioners and Latin rite friends about how Orthodox Pascha is calculated. Surprisingly it’s also allowed voice to be given to that same pious legend about the paschalion told among the Orthodox so let me deal with that first: the legend that Orthodox Easter must come after the Jewish Passover is simply untrue. It’s also something that was condemned in the first Council of Nicea.
Pascha and Pesach
In the 1st two centuries of the Christian Era there were two ways to date Easter: among some communities that were predominantly Jewish, the Resurrection was always celebrated on the 14th day of the month of Nisan – ניסן – no matter what day of the week it was. In fact, the entire paschal cycle of Death and Burial and Resurrection seems to have been commemorated in a community meal much like the Passover Seder on that night (beginning at Sunset the night before). Some have suggested that the Peri Pascha of St Melitos of Saedis is the “Passover Hagada” of that community. Still linked with 14 Nisan, communities that were mostly of Gentiles celebrated on the Sunday following that date.
These two traditions functioned side by side peaceably. It seems strange to us now, used to Easter always being Sunday, but it’s no different from Christmas which we celebrate on the 25th no matter what day of the week it is.
However, the Jewish calendar is a hybrid solar-lunar calendar. Its months are based entirely on the lunar cycle and this cycle does not match with the solar cycle at all. Prior to 358 AD, there was a tradition of looking for grain ripening to decide when it was time for Passover. When the barley reached a certain degree of ripeness (called, “aviv”) then the next full moon would be Passover. If the barley was not ripe enough at the end of the usual time, then a second month was inserted! This gets complicated – is it only barley in Israel? If the weather is bad, can we use the barley elsewhere to time it? How do we get news to the ever-widening diaspora of the Jewish People that Passover is coming? The Jewish community, with a nudge from Hillel II, instituted a fixed calendar in 358 AD it was not one-and-done though. It was a process of evolution and adoption. The lunar and solar cycles take 19 years or so to return to exactly the same place. To account for this the Jewish calendar, every once in a while, inserts a “leap month” which brings things closer to alignment as needed – but this is not based on barley, only on solar-to-lunar timing. This constant tinkering, common to all hybrid calendars, is the source of the problem that follows.
Imagine being a Christian at this time, waiting to hear from the local synagogue that Passover was this month on the full moon. Then you’d need to get ready for Easter as well.
At some point, it was evident to the Gentile communities that using the Jewish calendar to calculate the feast occasionally gives rise to some solar years (where solar = the “real” years) without a feast in the “real” twelve months. (I use this language to show the culture clash only – and that’s what it was: a culture clash.) What should we do if using the Jewish Calendar gives us one “real” twelve-month year with no Easter? Or one “real” year with two Easters? These two traditions stayed in communion, both produced saints and were included in the patristic commentary that gave us the scriptural canon and the oral traditions of the Church. But then the Jewish community began adopting a new calendar. What now?
Among all the questions of Christological Orthodoxy at the first Council of the Church was the question of Easter. It seemed good to the gathered bishops that the entire Church should celebrate this one feast together on the same day. It was not only decided to only use the Roman calendar (entirely on the solar or “real” year) but it was actually forbidden to use the Jewish Calendar in the calculation at all. This deals with the pious legend I mentioned earlier: Easter does not have to come after the Jewish Passover. The 14th Day of Nisan does not enter into the calculation at all.
Nicea set the feast of Easter to be always a Sunday. It was set to be the First Sunday after the First Full Moon after the Vernal Equinox. There were still a couple of problems.
The first problem with this calculation is solar. Unlike the Winter Solstice (on the shortest day) or the Summer Solstice (longest day), the Equinox is not very self-evident. Nearer to the equator (where most of the Church was located) even the Solstices are not very evident for most of the days are nearly the same length. Thus all these solar events are pegged to calendar dates that we still use: they are all on the 21st of a month: 21 December, 21 March, 21 June, and 21 September. We use these dates now even though we understand by virtue of more-recent astronomy that the actual equinoxes or solstices can vary slightly, moving back and forth from the 20th through to the 22nd of each month. Thus Easter is always the first Sunday after the first full moon after 21 March.
The second problem is lunar: when is the full moon? Early on the calculation of the full moon was assigned to the Patriarchate of Alexandria. It was universally recognized that they had the best astronomical resources. So a letter from the Patriarch announced which lunation would include the all-important full moon for the Christian feast. Then each local church would set the date of their celebration even in communities – Egypt or India for example – that used a different calendar. It had been recognized in the Greek world (long before Rome took over) that the moon moved in a very predictable cycle of 19 years. This was known as the Metonic cycle. This means that the dates of the full moon can be predicted well in advance. Lists of these dates were published. Everyone could do their own calendar now.
If you know the date of the moon, you only need to know the Sunday date and thus Easter can always be known. So, very early on complex tables were produced allowing one (anyone who was literate, that is) to look up a year and see exactly when Easter would be. Easter Tables are still published in prayerbooks. It’s a nerdy thing to use. They note the date of the Full Moon (called the Paschal Moon, even though it has nothing to do with Nisan) and a series of letters note the days of the week.
So it was decided to use the 21st of March as a set date and to use the Metonic Tables as set dates. This was to be easier than observational astronomy which could be complicated by weather, etc.
All of these dates were calculated on the Roman calendar which – at the time of Nicea – was the calendar produced by Julius Cesar! It was done by the best astronomers of his day. Everything worked well in the Church with this system for nearly 1100 years.
Why the Julian Calendar keeps slipping
The Julian Calendar had a year of 365 days exactly. Every four years without exception a day was added to February making the fourth year 366 days long. The problem is that the need for a “leap day” is not exactly every 4 years. Thus, over a thousand years or so, the Julian calendar was slipping out of alignment with the actual solar cycle. In fact, it had already slipped a bit even by the time of Nicea: culturally, the solstices and equinoxes were celebrated on the 25th of the month even though everyone “knew” they were “really” on the 21st. That Nicea used the 21st instead of the 25th shows that they were all about using the current science.
Right now the Julian Calendar has slipped 13 days behind the Gregorian calendar.
Here’s the reason that we have the issue of two Easters:
Orthodox Easter is still the first Sunday after the first full moon after 21 March. But what the Julian calendar calls March 21st is, for the Gregorian calendar, April 4th. That’s the solar problem.
The lunar problem is a bit more subtle. The observable full moon – the astronomical full moon – is not used. Rather it’s the one predicted by the Metonic Cycle. When Pope Gregory corrected the Solar Calendar he made one more change: he recalculated the tables for the Metonic Cycle, bringing them more in line with observable reality at his time. Thus Gregorian Easter is based on two dates somewhat closer to what they claim – the equinox and the full moon. The Orthodox response was “the Pope has no power to tell us what to do.” They kept their calendar AND they kept their Metonic tables so even on years when the predicted full moon is after the 4th of April – as in 2023 – there is a difference of a week or two between Easter and Pascha. Next year, the Gregorian Full Moon is before the 4th, so the Julian folks have to use the next lunar cycle and thus Pascha is 5 weeks after Easter!
Frankly, my dear Scarlet…
Nicea had a good idea: all Christians everywhere should celebrate the Feast of Feasts on the same day. Using the best science of the day the council made some choices. But the rule was we should all be on the same day.
I would love to get back to that, even if it means using a calendar that’s 14 days behind.
Updated here 4/17/2023
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