Julian Calendar Easter

[Kmon23]

I understand Orthodox and some Eastern Catholic churches celebrate Pascha on the Julian Calendar. It’s the first Sunday after the first full moon after the Vernal Equinox for both cases right?

For the Gregorian Calendar, Vernal Equinox was March 20 (21?), full moon was March 23, so Pascha Sunday is March 27 as expected.

For Julian, Vernal Equinox is March 21 but is lagging 13 days so is April 3 on the Gregorian Calendar, first full moon after this is April 22, so the first Sunday after that is April 24. Yet Pascha is May 1?

What mistake am I making in calculating Old Calendar Pascha? Is there difference in calculating Pascha between the two I’m forgetting?

 

[Brendan]

That was something that I never quite understood. Nicaea was pretty specific. Easter was to be celebrated on the first Sunday after the first full moon after the vernal equinox.

the occurance of the full moon and the vernal equinox are independent of calendar. They are simply astronomical events.

So the only remaining factor to agree on is when "Sunday’ happens. All that is required there is do agree on a meridian. If the vernal equinox (which is a very specific moment) happens on, say Monday using this meridian, then the following Sunday is Easter\Pascha.

Either the Prime Meridian, or Jerusalem would be obvious choices.

But what Easter\Pascha clearly does NOT depend on is a particular calendar, Julian or Gregorian.

 

[Kmon23]

the occurance of the full moon and the vernal equinox are independent of calendar. They are simply astronomical events.

It was my understanding that the vernal equinox actually is dependent on the calendar. Instead of having it as an astronomical event, it was established as an ecclesiastical date of March 21 in Nicaea (correct me if I’m wrong). Hence why Eastern churches that follow the Julian Calendar have no serious qualms about the vernal equinox since it’s technically an ecclesiastical date, not entirely an astronomical one.

It’s also why the Gregorian Calendar was even proposed, since Rome wanted the ecclesiastical date of the Vernal Equinox to be closer to the astronomical one.

 

[malphono]

I understand Orthodox and some Eastern Catholic churches celebrate Pascha on the Julian Calendar. It’s the first Sunday after the first full moon after the Vernal Equinox for both cases right?

For the Gregorian Calendar, Vernal Equinox was March 20 (21?), full moon was March 23, so Pascha Sunday is March 27 as expected.

For Julian, Vernal Equinox is March 21 but is lagging 13 days so is April 3 on the Gregorian Calendar, first full moon after this is April 22, so the first Sunday after that is April 24. Yet Pascha is May 1?

What mistake am I making in calculating Old Calendar Pascha? Is there difference in calculating Pascha between the two I’m forgetting?

Without a small complication when calculating Easter on the Julian Calendar, you’re thought would be right. I don’t have the patience to go searching for it, but IIRC it has to do with the first Sunday after the first Friday after the full moon. Since the full moon is Friday, it pushes Easter a week out. If the full moon were the day before (April 21), Easter would fall on the 24th. As I see it, Easter should always fall during the month of April, IOW not in March nor in May, and IMO it’s incorrect to disregard the day of the full moon itself. But of course it is what it is and my opinion makes no difference.

 

[Cavaradossi]

I understand Orthodox and some Eastern Catholic churches celebrate Pascha on the Julian Calendar. It’s the first Sunday after the first full moon after the Vernal Equinox for both cases right?

For the Gregorian Calendar, Vernal Equinox was March 20 (21?), full moon was March 23, so Pascha Sunday is March 27 as expected.

For Julian, Vernal Equinox is March 21 but is lagging 13 days so is April 3 on the Gregorian Calendar, first full moon after this is April 22, so the first Sunday after that is April 24. Yet Pascha is May 1?

What mistake am I making in calculating Old Calendar Pascha? Is there difference in calculating Pascha between the two I’m forgetting?

Just as there is an ecclesiastical date for the equinox, there is also an ecclesiastical date for the full moon, which rotates on a 19 year cycle. This date is usually several days later than the astronomical full moon.

 

[dvdjs]

It was my understanding that the vernal equinox actually is dependent on the calendar. Instead of having it as an astronomical event, it was established as an ecclesiastical date of March 21 in Nicaea (correct me if I’m wrong).

This idea is in fact incorrect. At the time that the Julian was established, the vernal equinox was ~Mar25 (and winter solstice Dec 25). By the time of Nicea there was already a lag of about 4 days; the astronomical equinox was Mar 21. So the date was shifted to reconcile the calendar and the equinox, not to define some artificial equinox day.

The surviving letter of the Emperor announcing the definition of the council makes its completely clear that “vernal equinox” in the calculation of the date of Pascha is the actual, astronomical equinox. He advances the idea that other churches should follow Alexandria in determining the date of the equinox because they has the best astronomers. That recommendation fell on deaf ears, however. Even in the immediate aftermath of Nicea, various churches made their own observations, some better some worse, and had different dates for the equinox.

 

[Vico]

I understand Orthodox and some Eastern Catholic churches celebrate Pascha on the Julian Calendar. It’s the first Sunday after the first full moon after the Vernal Equinox for both cases right?

For the Gregorian Calendar, Vernal Equinox was March 20 (21?), full moon was March 23, so Pascha Sunday is March 27 as expected.

For Julian, Vernal Equinox is March 21 but is lagging 13 days so is April 3 on the Gregorian Calendar, first full moon after this is April 22, so the first Sunday after that is April 24. Yet Pascha is May 1?

What mistake am I making in calculating Old Calendar Pascha? Is there difference in calculating Pascha between the two I’m forgetting?

Catholic Encyclopedia:

The second stage in the Easter controversy centres round the Council of Nicaea (A.D. 325). Granted that the great Easter festival was always to be held on a Sunday, and was not to coincide with a particular phase of the moon, which might occur on any day of the week, a new dispute arose as to the determination of the Sunday itself. The text of the decree of the Council of Nicaea which settled, or at least indicated a final settlement of, the difficulty has not been preserved to us, …

The Alexandrians, on the other hand, accepted it as a first principle that the Sunday to be kept as Easter Day must necessarily occur after the vernal equinox, then identified with 21 March of the Julian year. This was the main difficulty which was decided by the Council of Nicaea. Even among the Christians who calculated Easter for themselves there had been considerable variations (partly due to a divergent reckoning of the date of the equinox), and as recently as 314, in the Council of Arles, it had been laid down that in future Easter should be kept uno die et uno tempore per omnem orbem, and that to secure this uniformity the pope should send out letters to all the Churches. The Council of Nicaea seems to have extended further the principle here laid down. As already stated, we have not its exact words, but we may safely infer from scattered notices that the council ruled:

• that Easter must be celebrated by all throughout the world on the same Sunday;
• that this Sunday must follow the fourteenth day of the paschal moon;
• that that moon was to be accounted the paschal moon whose fourteenth day followed the spring equinox;
• that some provision should be made, probably by the Church of Alexandria as best skilled in astronomical calculations, for determining the proper date of Easter and communicating it to the rest of the world (see St. Leo to the Emperor Marcian in Migne, P.L., LIV, 1055).

This ruling of the Council of Nicaea did not remove all difficulties nor at once win universal acceptance among the Syrians.

…

What is perhaps most important to remember, both in the solution adopted in 525 and in that officially put forward at the time of the reform of the Calendar by Gregory XIII, is this, that the Church throughout held that the determination of Easter was primarily a matter of ecclesiastical discipline and not of astronomical science.
Thurston, H. (1909). Easter Controversy. In The Catholic Encyclopedia. New York: Robert Appleton Company. newadvent.org/cathen/05228a.htm

 

[Expatreprocedit]

Just as there is an ecclesiastical date for the equinox, there is also an ecclesiastical date for the full moon, which rotates on a 19 year cycle. This date is usually several days later than the astronomical full moon.

I truly do not understand the notions of an “ecclesiastical date” for the vernal equinox, or an “ecclesiastical date” for the full moon.

 

[Vico]

I truly do not understand the notions of an “ecclesiastical date” for the vernal equinox, or an “ecclesiastical date” for the full moon.

Read post #7 that “the determination of Easter was primarily a matter of ecclesiastical discipline and not of astronomical science”.

 

[Expatreprocedit]

Read post #7 that “the determination of Easter was primarily a matter of ecclesiastical discipline and not of astronomical science”.

I did. My problem is not with an ecclesiastical determination of Easter but with, as I said, the ecclesiastical determination of the vernal equinox and the ecclesiastical determination of the full moon.

 

[Vico]

I did. My problem is not with an ecclesiastical determination of Easter but with, as I said, the ecclesiastical determination of the vernal equinox and the ecclesiastical determination of the full moon.

You mean the idea of a tabular dates for the two verses the astronomical? Once observed and adjusted, the practice of using tables was adopted for the Jewish Passover and for Christian Easter. About 500-600 A.D., the Jewish calendar rules were published and thence the calendar was computed rather than observed, and is not as accurate. This is attributed to Hillel II.

It is not an astronomical but ecclesiastical rule.