Why Greek Orthodox and Catholic Easter Will Never Coincide After 2700

By Phillip Chrysopoulos 

This year, Catholic and Greek-Orthodox Christians — who use different liturgical calendars — celebrated Easter one week apart, with the former being on April 1 and the latter April 8. In 2017 the celebration coincided exactly.

In 2017, Easter came at the same time for both denominations, something that will happen again in 2025. Until 2020, Catholic and Greek Orthodox Easters will continue to fall one week apart.

However, for purely astrological reasons, the difference between the celebration of Easter for the two denominations will be getting wider by some years.

And from 2700 and on, the celebration of Easter for the Greek Orthodox Church and the Catholic Church will never coincide again.

Altogether, in the whole 21st century, the celebration of Easter will be common 31 years, but every forthcoming century this will happen more and more rarely.

The last time Easter celebrations will coincide is estimated to be in 2698. From then on, Orthodox and Catholic Christians will never celebrate the Resurrection of Christ together again.

Easter and the Western calendar

The First Ecumenical Synod in 325 AD decided that Easter would be celebrated on the first Sunday after the first full moon of spring. If this full moon occurs on Sunday, then it will be celebrated the next Sunday. Thus, the Christian Easter would never coincide with the Jewish Passover. At the same time the celebration of Christian Easter was clearly associated with an astronomical phenomenon, the spring equinox and the first full moon of spring.

In order to calculate the date of Easter, the date of the first full moon and then the first Sunday after the full moon had to be found. The First Ecumenical Synod instructed the Patriarch of Alexandria to inform the other churches the Easter day after the date of the first full moon was calculated with the help of the astronomers in the Egyptian city.

The calendar that was in force at the time of the First Ecumenical Synod was the Julian one that Julius Caesar had instituted in 45 BC with the help of the Alexandrian astronomer Sosigenis. The latter, based on the calculations of Hipparchus (who a century ago had estimated with impressive accuracy that the solar year had a duration of 365.242 days), established a calendar with 365 days, and in every fourth year (the “leap year”) one more day was added.

However, the Julian Calendar had a small error, because the duration of the solar year is in fact 365.242199 days. Every four years, this small error reaches 45 minutes, and every 129 the minutes add up to a day. As a result, the Spring Equinox is coming more and more early.

Thus, while the Spring Equinox at the time of Christ occurred on March 23, in 1582 AD it had reached March 11.

Then Pope Gregory II instructed astronomers Christoforos Klavios and Luigi Lilios to make a calendar reform. Oct. 5, 1582 was renamed Oct. 15 to correct the error that had accumulated over the past 11 centuries and the Spring Equinox to return to March 21, as it had been during the First Ecumenical Synod.

The New, or Gregorian, Calendar was adopted by the Catholic states of Europe in the next five years, and by the Protestants much later. Due to an even stronger reaction by the Orthodox Church to the Gregorian Calendar, the Julian Calendar remained in force in all Orthodox States until the 20th century.

Greece and the Gregorian calendar

In Greece, the Julian Calendar was replaced by the Gregorian on Feb. 16, 1923, with the date changing to March 1st. That is, 13 days have been removed since 1923, because of the 10-days error between the Gregorian and the Julian calendars since 1582 and another three days for the difference between the adoption of the Gregorian calendar by the West and its adoption by the Greeks three-and-a-half centuries later.

In 1924, the Greek Orthodox Church accepted the ecclesiastical calendar be identical with the civil calendar and to apply for immovable holidays, but not for the Easter Calendar and for the mobile holidays, which are still calculated on the basis of the Julian or Old Calendar.

But the difference in the celebration of Easter between Orthodox and Catholics is not only based on the error of the Julian Calendar but also on the error of the so-called “Metonic cycle”, named after Greek astronomer Meton of Athens of the 5th century BC.

The Metonic cycle is a period of close to 19 years, which is almost a common multiple of the solar year and the synodic (lunar) month. The Metonic cycle was used by the Christian astronomers of Alexandria, on the basis of which the Orthodox Church continues to count the dates for future spring full moons.

On the 13 days of the Julian Spring Equinox, the error of the 19-year Metanic cycle – which from 325 AD to the present time amounts to four to five days – must be added. As a consequence the Metonic (or Julian) full moon is calculated four to five days later than the actual one.

The Greek Orthodox Church continues to use the Old Julian Calendar and the Metonic cycle to determine the date of Easter. Thus, Orthodox Easter is often celebrated not on the first Sunday after the full moon, but on the next or after the second full moon, instead of the first Sunday after the first Spring full moon, as the Nice Synod had decided.

Catholics celebrate Easter according to the rule of the First Ecumenical Synod, but their Spring Equinox and the spring full moon are calculated according to the New Gregorian Calendar, also taking into account the Metonic error. So the Gregorian-Catholic full moon is much closer to the astronomical one (often coinciding or having only one day difference) than the Julian-Orthodox.

It is fairly common that Orthodox and Catholic Christians to celebrate Easter together, when both the Gregorian and the Julian-Metonic Easter moon fall from Sunday to Saturday of the same week (as long as it is after April 3 and two full moons), so the next Sunday is Easter common for both.

However, after 2700, due to the accumulation of the Metonic error for almost seven centuries the Julian and the Gregorian full moon will never coincide in the same week again, so there will be no common Easter again.

Reprinted with permission from the Greek Reporter.


  1. The simplest resolution: for Rome to determine to use Julian-Metonic calculation. The reason it’s the simplest is that any other resolution between Rome and the East would require the Russian Orthodox Church to agree to a change, which is a harder thing to imagine.

    1. I am not sure I am favor of such as change. But if it were to occur, there would be a few benefits. Easter would be pushed later into April and occasionally into May, so there would often be a greater space between the Christmas cycle and Ash Wednesday. Also OT would be slightly shorter post Pentecost which helps to provide a bit more balance to the liturgical year.

      A later Easter would probably help to avoid snow, but at the same time, if the Paschal Vigil is to be held in it’s entirety during the dark, then the start time would be pushed later as well. But that could help attendance at the Maundy Thursday evening service.

      1. “A later Easter would probably help to avoid snow, but at the same time, if the Paschal Vigil is to be held in it’s entirety during the dark, then the start time would be pushed later as well. But that could help attendance at the Maundy Thursday evening service.”

        In the Northern Hemisphere….

        PS: For them that love minutiae: https://blogs.ancientfaith.com/roadsfromemmaus/2015/03/31/no-pascha-does-not-have-to-be-after-passover-and-other-orthodox-urban-legends/

      2. Yes, though the Southern Hemisphere tends to have significantly less snow b/c the population centers tend to be significantly close to the equator, so light is the main issue.

        On another note, as global warming continues unabated, for many places in the U.S., Pascha will continue to get warmer and warmer even if the criteria for calculating Easter remains constant. 90° Easters may become common in the Northeast and Midwest for example. So for the Northern Hemisphere, later dates would only increase that trend.

        But the Southern Hemisphere would benefit from having have more temperate Easters if the date of Pascha was moved forward into later April and earlier May.

        But since the powers that be on the world stage are trying their best to make sure we don’t make it out of this century alive, we may be wasting our time speculating on future Easters.

      1. Btw, in such event, would Protestant denominations (and traditionalist Catholic sects) that refuse to follow such a decision would be adhering to an Old New Easter calendar?

      2. I wonder what would happen to Catholic attendance on Easter in places where the non-Catholic majority didn’t go along with the change. Everywhere I’ve ever lived, the school districts (K-12) attach spring break to Easter and give Good Friday off, and many local businesses and organizations have Easter egg hunts and other events. Would many of the “Christmas and Easter” Catholics still attend Mass for Easter if it didn’t coincide with the wider culture’s celebration of Easter?

        BTW, I think the SSPX wold go along with a change if the Church did. The holdouts would probably be the much smaller independent and Sedevecantist groups.

  2. Once again, it is not “Greek Easter” or “Russian Easter” or even “Orthodox Easter.” It is Pascha celebrated according to the Julian calendar. Lest anyone forget, the majority of the world’s Eastern Catholics also keep Pascha on the Julian reckoning and not the Gregorian. Horror of horrors! All Catholics don’t even celebrate on the same day.

    1. If current geopolitical trends are any indication, I think we’ll be overrun by the Fremen long before then.

      1. You, on the other hand, will end your days in agony on Salusa Secundus for your treachery.

  3. “However, for purely astrological reasons…”


    This is astronomy, not astrology.

    I would surely hope that a common celebration of Easter would be taking place on Planet Earth long after 2698AD. If not, we would be able to diagnose some serious flaw in how Christians have handled ecumenism in the coming seven centuries.

    I’m not sure about Giedi Prime, and I don’t think we will actually reach the planets of 36 Ophiuchi in this millennium, but if human beings do colonize space, including planets, moons, and asteroids, it is likely that each world will eventually use its own astronomical calendar instead of Earth’s. Would Easter on Mars be every 22 months, and Lent extended to seventy days? Or would the liturgical year end with the 79th week in Ordinary Time?

    1. There is no real evidence that such radical endulturation will occurr on other planets. Precedent is against it, since the Northern Hemishpere dates are adopted in our Southern Hemisphere without any acknowledgement of the differences. Jesus was born as an earthling, and that might be a good enough reason to retain the use of earth years on other planets. (Heresy 3001, we should celebrate Easter on the Sunday after the first full moon in spring according to the seasons and moons of our native planets instead of those of Earth)

      And what will become of the Urbi et Orbi address? Will the orb become the universe instead of the earth? Or the Earth become the urb because it was the first densely populated place?

      And what about the planets in the Trappist system? Will we need to consult with the monks about how we handle these thing?

      1. Well, it’s not defined if there would be any need for worship outside of Earth except by human beings. Medieval scholastics did probe the issue of plural worlds, and I believe one offspring of that speculative theology was the realization that the Hypostatic Union of human and divine natures in the Second Person of the Most Holy Trinity would not necessarily preclude other such unions *if* so provided by God for beings in other worlds who are, obviously, not necessarily descendants of Adam and Eve, et cet….. (TL DR version: Catholic theology can accommodate non-earth intelligent life more readily than a fundamentalist theology.)

      2. If we make it to the Trappist-1 system they would have their own bishop(s), and presumably Patriarch. They would have their own Urbi et Orbi tradition.

        As for the use of Earth years, what do you suggest? Years as counted by interstellar travelers, even if the affects of relativity have knocked things out of kilter from Earth?

    2. What if the planet has a really short year, like 10 weeks or so? You could have a “greatest hits” sort of liturgical year. No rest for the choir or volunteer church decorators, though.

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