Eastern Orthodox Easter

It turns out that this day is more accurately Easter, or at least the more astronomically accurate Easter.*

The complicated calculation goes like this: Easter falls on the first Sunday after the first full moon on or after the vernal equinox. But the Eastern Orthodox Church, for some reason, uses the astronomical full moon and the actual equinox while, strangely, Western Christianity uses a fixed date (March 21) for the equinox, and something called the paschal full moon (which may or may not be the actual full moon), derived from a table of ecclesiastical moons.

Who knew?

The Eastern Orthodox system is also more logically correct. In the West, Easter sometimes precedes Passover, but the Orthodox calculations ensure that Easter always follows Passover – as the resurrection followed the last supper.

You’d think they’d all want to get together. In 1963, the Second Vatican Council suggested Easter be fixed at the second Sunday in April, if all the Christian churches could agree – but nothing happened. Then, in 1997, the World Council of Churches proposed that both East and West use the most sophisticated astronomical calculations for their joint formula – but nothing happened.


*Turns out I’m quite wrong about this! (See Mockingbird‘s comment, who clearly knows a lot more about this than I do.)

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3 Responses to Eastern Orthodox Easter

  1. Mockingbird says:

    You write:

    ” But the Eastern Orthodox Church, for some reason, uses the astronomical full moon and the actual equinox”

    This is false. The astronomical equinox was at 11:44 universal time March 20, 2009. You can verify this at the U.S. Naval Obervatory’s seasons tables:


    The astronomical full moon was at 14:56 universal time on Thursday, April 9, 2009. You can verify this at the USNO’s primary phase tables:


    Hence “the first Sunday after the first full moon on or after the vernal equinox” was the Sunday following April 9, or April 12. So if the eastern paschalion truly were using the astronomical method, it would have set eastern Easter to the same date this year as western Easter.

    Orthodox bishops, at a meeting in 1923, agreed to use the astronomical moon and equinox to compute Easter. But the agreement was never implemented.

    The eastern churches, except that of Finland, use the old Julian computus to calculate Easter. The Julian equinox is fixed, like the Gregorian, at March 21, which corresponds to April 3 Gregorian. And the Julian full moons are 4 or 5 days behind the Gregorian. The western Paschal full moon was on Friday, April 10, 2009, a day after the astronomical full moon. The eastern Paschal full moon was on Tuesday, April 14, 2009, five days after the asteronomical full moon. How is that “astronomically accurate?”

  2. celebratingtime says:

    Thanks, Mockingbird. I read this here, but even though they call themselves “FactMonster” I guess they’re incorrect.
    But why does the Orthodox Church use the Julian calendar – is it because the Gregorian came from a Roman Catholic pope?

  3. Mockingbird says:

    The story that the eastern churches compute Easter using precise astronomical computations referred to the meridian of Jerusalem is based on an accurate fact: In 1923, Eastern Orthodox Bishops agreed to do just that. But their agreement was never implemented. (The “solar part” of their agreement became the Revised Julian Calendar, which was implemented in some places. The “lunar part”, the revised Paschalion, was simply dropped.) But the tale doesn’t end there. The fact of the bishops’ agreement was reported in the western astronomical literature, and made its way into a standard reference work, the Explanatory Supplement to the American Ephemeris and Nautical Almanac. The report went like this:

    At a meeting of a Congress of the Orthodox Oriental Churches held in Constantinople in May, 1923, the Julian Calendar was replaced by a modified Gregorian calendar…[in which] Easter is determined by the astronomical Moon for the meridian of Jerusalem.

    This was technically true. The Julian calendar was replaced at the meeting. But it wasn’t replaced in any of the bishops’ diocese after the bishops got home. Western readers, however, reading the Explanatory Supplement with no knowledge of Eastern Orthodox ecclesiastical or cultural politics, simply assumed that the bishops’ agreement must have gone into force. Thus was born the tale that the Orthodox churches use the astronomical method.

    As to why the eastern churches continue to use the Julian calendar notwithstanding its manifest flaws, I think the short answer is that it is too old and traditional to change easily. Even in the western church, Roger Bacon was complaining in the 13th century about the drift in the Julian lunar tables. “Any farmer”, he wrote, “can see in the sky” that the tables were off by several days. But nothing was done for another 300 years.

    An Antiochian Orthodox article on the calendar question can be found at


    Notice how the article states right at the beginning, “In stating facts about methodology, it is not the author’s intent to propose a revision to the current dating methods,” even though that is precisely what the author does. Reading between the lines, I get the impression that any talk of changing the Easter cycle raises strong emotions. In addition, various excuses are offered for maintaining the Julian calendar and paschalion. Some like to state that Easter must come always after the Jewish Passover as computed by the modern Hebrew calendar. This is not true, but it has been taught since the 12th century, and some people have become accustomed to it. The most bizarre excuse I have encountered for keeping the Julian calendar is that the inaccuracies will cause Easter to cycle into the norther hemisphere’s fall season, so that Orthodox Christians in the southern hemisphere can finally have Easter in their spring season.

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