Something that’s interesting (maybe?) is the date for Easter is weird because it was originally based on a date in the Jewish calendar (it was the first Sunday after 15 Nisan which is the first day of Passover) and the Jewish Calendar is lunar (this is why Jewish holidays shift around on the Gregorian Calendar year by year). It has changed some since then to distance it from Passover but this is why is doesn’t have a fixed date.
More precisely, the Jewish calendar, like the Chinese calendar, is sol-lunar. That means that a year sometimes has 12 months and sometimes 13, so that on average, the year stays the same length as a solar year. This is in contrast to a purely lunar calendar, like the Muslim calendar, which always has a 12-lunar-month year, and which therefore slides out of synch with solar calendars over time.
Of course, some religions do base their official calendars on actual astronomical observations (though of course, these can be predicted extremely well, with modern astronomical knowledge).
I don’t think that’s the reason it was changed. It was changed to standardize it across Christianity (narrator: it failed). The Last Supper is a part of Easter and a prototype of Communion, one of the two universal rites of Christianity. It is also widely considered by Christians to be a part of Passover and necessarily Jewish.
Aren’t all the computations above for determing the date of Easter for Western Christianity? Eastern Christianity’s Easter is generally later, but this year the two branches of Christianity celebrate Easter at the same time.
The first Sunday after the first full moon following the spring equinox. Unless that day is a Sunday in which it’s a week later.
Probably the earliest Easter in my lifetime was 2008. It was March 22. and lands then roughly every ninety years.
Orthodox Easter is on different dates mostly because their ecclesiastical calendar is the old Julian calendar.
My spectacles are malfunctioning; the charts say 2066 is my next birthday/Easter confluence. Can I make those extra six years? How much Cadbury you got?
Yes, that’s right. It is not the actual full moon. The Roman Catholic Church has an ecclesiastical algorithm to compute the date of the Paschal Full Moon. It looks a bit like the instructions on a tax form. Instead of writing out an equation, a set of steps is defined that involves things like a correction factor for each year and so forth. The advantage is that anyone can do the computation and no matter where they are, they will arrive at the same date. The date of the actual full moon depends on your time zone, so this algorithm removes that problem.
My son was born on Oct. 10. When he was still a baby, I checked; he will turn 21 on Yom Kippur. That means champagne at the break-the-fast. If it were a day earlier, we’d be pouring him into his seat (and let’s be honest: probably his father too) at Kol Nidre, after a keg at the last meal before the fast started.
My birthday is nowhere near my bat mitzvah portion, because it is January 7, and I turned 13 two years after the Blizzard of 78. People over 55 get it. My mother insisted on waiting until spring before spending thousands of (1980) dollars on a party only to have all our relatives’ flights canceled due to weather, and our local guests even afraid, or unable to venture out.
As I learned it, the first Sunday after the first Monday after the first full moon after the vernal equinox.
That can’t be right, because then you’d never be able to get one before the very last days of March. Even if you get that Monday right away, you’d still need to wait nearly a week after the Equinox.
I think that might be the Orthodox calculation. I honestly don’t know if it is accurate.
I see that Ukraine and the Ukrainian Orthodox Church has recently changed Christmas to occur on Dec. 25th instead of following the same (Julian) calendar as the Russian Orhtodox church. Not sure if this applies to Easter as well.
Islamic authorities in each country have something like a “moon estimation committee” to determine the last day of Ramadan each year, and they don’t all set the same date, although the variation is small.
Related question; this year, the Western and Eastern churches have Easter on the same date but not in other recent years. Any idea why they coincided?
2024 date
March 31 (Western)
May 5 (Eastern)
2025 date
April 20 (Western)
April 20 (Eastern)
2026 date
April 5 (Western)
April 12 (Eastern)
2027 date
March 28 (Western)
May 2 (Eastern)
I’m not sure there’s a satisfying answer to “why” they coincide. The Western and Eastern churches use different algorithms, both rather complicated, and sometimes they produce the same date. This graph shows the dates in both churches for 100 years starting in 1950. You can see that it’s not uncommon for them to be on the same date; it looks like it happens in about a quarter of the years.
As I understand it, the algorithms are mostly the same, aside from some fine details, and the biggest difference is that they disagree on when “March 21” is. But if the first full moon after March 21 happens to be more than two weeks later, both churches will be using the same full moon, and so have the same Easter.
I saw an online article once talking about how the common dates will gradually be less common, because the calendars will keep on diverging. If I remember correctly sometime in the 2600’s they will be far enough apart that they won’t be able to be on the same date.
Saturday’s Washington Post has an interesting article about how and why Western and Orthodox Easters match this year and will match again in 2028. It doesn’t precisely describe the exact calculation, but has an interesting take:
I read this to mean that Easter would always be on the same day of the calendar, such as Christmas is always December 25th, but on a Sunday, just as Thanksgiving in the US is always on a Thursday. Perhaps the first Sunday in April? I doubt that they change will happen anytime soon.
Here’s the WaPo gift article (hope it works):
If they want everybody to agree, is there some reason not to have it on the first Sunday after the (actual) full moon on or after the (actual) equinox?
One difficulty with that is the astronomical spring Equinox and the astronomical full moon are both at specific points in time. Either might occur on March 22 in Europe and March 21 in the US due to time zone difference. If that also happens to be a Sunday or Saturday (depending on whether "after’ means “strictly after” or “on or after” there would be disagreement. I suppose you’d could define it as equinox or full moon in Rome (upsetting Protestants and Eastern Orthodox churches). Better would probably be Jerusalem time, I suppose.