On calculating Easter

March 14, 2008

Although for most Christians Easter is just around the corner, for the Orthodox Church Lent began this week; there is a five-week disparity this year between the dates of Easter (April 27th for the Orthodox, March 23rd for everyone else). When I was younger I asked my mother why the Orthodox Easter and the Protestant and Catholic Easter fall on different dates, and was given the following explanation: for the Protestants and Catholics, Easter falls upon the first Sunday after the first full moon after the vernal equinox; for the Orthodox, Easter is the first Sunday after the first full moon after the vernal equinox after Passover. As a rule of thumb, I have found this explanation always to work (e.g., Passover begins this year on the evening before April 20th, which also happens to be a full moon); however, I have also learned that, as an explanation for why the differences exist between the Orthodox Church and other churches in their calculation of the date of Easter, it is erroneous. The difference between the dates of Easter arises from the fact that the Western churches calculate this date according to the revised, Gregorian calendar while the Orthodox Church calculates Easter according to the old Julian calendar. That is to say, all the churches observe the rule, established by the Council of Nicaea in the fourth century, that Easter be celebrated on the first Sunday after the first full moon after the vernal equinox; but they identify differently the day on which the vernal equinox occurs. Although the vernal equinox — the moment when day and night are exactly equal, or, to speak in Ptolemaic terms, when the sun, in its annual journey through the zodiacal belt, crosses the celestial equator, marking the beginning of Spring in the Northern hemisphere — actually occurs on March 20th this year, the Orthodox Church reckons “March 21st” as a fixed date for this astronomical event, and it reckons this fixed date according to the Julian calendar. Currently, the Julian March 21st is the Gregorian April 3rd, that is, roughly 13 days later than the astronomical equinox; over time, the discrepancy will continue to grow, at the rate of about a week per millennium, so that, if nothing else changes, Orthodox Christians in the year 6008 will be celebrating Easter in late May or June.

I subjoin an article on the effort to agree upon a common date of Easter; it is copied from the website of the World Council of Churches, http://www.oikoumene.org/?id=2677.

Towards a Common Date for Easter

World Council of Churches/Middle East Council of Churches Consultation
Aleppo, Syria
March 5 – 10, 1997

“Christ, our paschal lamb, has been sacrificed. Let us therefore celebrate the festival.”
1 Cor. 5:7-8.

I. The Issues

Background to this consultation

1. In the 20th century the churches have rediscovered a deep concern for Christian unity. They have expressed this in their efforts to find common ground on theological issues that have long divided them. They have learned to give common witness in a variety of ways. But despite this progress towards visible unity, many challenges remain. One very sensitive issue, with enormous pastoral consequences for all the Christian faithful, has taken on growing urgency: the need to find a common date for the celebration of Easter, the Holy Pascha, the feast of Christ’s resurrection. By celebrating this feast of feasts on different days, the churches give a divided witness to this fundamental aspect of the apostolic faith, compromising their credibility and effectiveness in bringing the Gospel to the world. This is a matter of concern for all Christians. Indeed, in some parts of the world such as the Middle East, where several separated Christian communities constitute a minority in the larger society, this has become an urgent issue. While there has been some discussion of this question, it still has not been given the serious attention that it deserves.

2. While the question of a common date for Easter/Pascha has been addressed at different times since the earliest Christian centuries, a renewed discussion of this issue has arisen in the present century in the churches of both East and West. It also has emerged in significant ways in the secular world. The question was put to the wider Christian world in a 1920 encyclical of the ecumenical patriarchate of Constantinople and addressed in a 1923 Pan-Orthodox congress, whose decision to revise their calendar unfortunately led to several schisms within the Orthodox churches. Around the same time, discussion was beginning in secular circles especially in Western Europe concerning the possibility of establishing a fixed day for Easter, such as the Sunday following the second Saturday in April, so as to facilitate commercial planning and public activities. In addition, proposals for introducing a new fixed calendar were being advanced, for similar utilitarian reasons. After World War II the context for discussion of such issues changed in several ways. International secular initiatives received little support. The churches were especially opposed to any calendar reform which would break the cycle of the seven-day week. On the other hand, many churches continued to express interest in the idea of a common day, whether movable or fixed, for the celebration of Easter/Pascha. The Orthodox returned to the paschal question from 1961 onwards, in the context of preparations for the Great and Holy Council of the Orthodox Church; the Constitution on the Sacred Liturgy of the Second Vatican Council (1963) gave renewed impetus in the Roman Catholic Church to discussion of this issue; and since 1965 the World Council of Churches has taken up the subject on a number of occasions.

3. In recent years, concrete steps have been taken in the Middle East, where Christians of so many traditions live closely together in a largely non-Christian society. The Middle East Council of Churches has been particularly active in encouraging and facilitating the celebration of Easter/Pascha on a common day. Two recent WCC consultations have taken up this concern. A consultation on “Christian Spirituality for Our Times” (Iasi, Romania, May 1994) proposed that “a new initiative be taken towards the common celebration of Easter.” Even more striking are the conclusions reached by a consultation “Towards Koinonia in Worship” (Ditchingham, England, August 1994):

Besides the work already done on baptism, eucharist and ministry, the churches need to address the renewal of preaching, the recovery of the meaning of Sunday and the search for a common celebration of Pascha as ecumenical theological concerns. This last is especially urgent, since an agreement on a common date for Easter – even an interim agreement – awaits further ecumenical developments. Such an agreement, which cannot depend on the idea of a “fixed date of Easter”, should respect the deepest meaning of the Christian Pascha, and the feelings of Christians throughout the world. We welcome all initiatives which offer the hope of progress in this important area.” (T.F. Best/D. Heller, eds., So We Believe, So We Pray: Towards Koinonia in Worship, Faith and Order Paper No. 171, WCC Publications, Geneva 1995, pp. 9-10.)

In view of the concerns expressed at these consultations, the Executive Committee of the WCC, meeting in Bucharest, September 1994, recommended that Unit I, “especially the Ecclesial Unity/Faith and Order stream and the Worship and Spirituality stream, give renewed attention to the subject of the common celebration of Easter, keeping in mind that in the year 2001, the dates of Easter according to both Eastern and Western calendars coincide.”

4. The present consultation, meeting in Aleppo, Syria, March 5-10, 1997, comes in response to this request. Sponsored jointly by Unit I of the WCC and by the Middle East Council of Churches (MECC), it brings together representatives of a number of communions which participate in the annual meeting of the Conference of Secretaries of Christian World Communions, representatives of the Eastern and Oriental Orthodox Churches, representatives of the MECC, and invited experts and staff. Together participants in the consultation enjoyed the hospitality of the Syrian Orthodox Archdiocese of Aleppo and experienced first-hand the commitment to unity of the Christian communities of this city. At a meeting with members of these communities, they listened to a call for removal of the painful sign of separation which differing dates for Easter/Pascha constitute. In an atmosphere of prayer and common study, participants considered the problem of a common day for the celebration of Easter/Pascha from various perspectives – theological, historical, liturgical, catechetical and pastoral. The consultation offers to all the churches the following observations and recommendations.

Christ’s resurrection, basis of our common faith

5. The apostolic faith of the Church is based on the reality of the resurrection of Christ. As St. Paul says: “Now if Christ is proclaimed as raised from the death, how can some of you say there is no resurrection of the dead? If there is no resurrection of the dead, then Christ has not been raised, and if Christ has not been raised, then our proclamation has been in vain and your faith is in vain.” (1 Cor. 15:12-14) Viewed as the ultimate victory over the powers of sin and death, the resurrection of the Lord is not only an historical event but also the sign of God’s power over all the forces which can keep us from his love and goodness. It is a victory not only for Christ himself but also for all those united with him (1 Pet. 1:3f). It is a victory which marks the beginning of a new era (Jn 20:17). The resurrection is the ultimate expression of the Father’s gift of reconciliation and unity in Christ through the Spirit. It is a sign of the unity and reconciliation which God wills for the entire creation.

6. As the apostles began their missionary activity, the resurrection was at the heart of their preaching (1 Cor. 15: 1-17, Acts 2:22-36, 1 Pet 1:3), and as the evangelists began to record aspects of the Lord’s teachings and ministry, the resurrection comes as the culminating event in their gospels. In every aspect of her life, the early Church was first and foremost the community of the resurrection. Thus the early Church’s life of worship focused on God’s reconciling love as manifested in the saving passover of Christ’s death and resurrection. The first day of the week became the preeminent day of the Christian assembly because it was the day on which the Lord rose from the dead (Jn 20:1, Acts 20:7). At the same time, this came to be known as the “eighth day,” a day of new creation and ultimate fulfillment. Each year too, Christians both remembered and experienced the continuing power of Christ’s passion and resurrection in a single but multifaceted celebration. This celebration also became the occasion for baptism, in which Christians shared in Christ’s passage from death to life, dying to sin and rising to new life in him. Therefore the behavior of Christians was rooted in their relationship with the risen Lord and reflected the new reality inaugurated by him (Col. 3:1-11).

Historical background to the present differences

7. The New Testament indicates that Christ’s death and resurrection were historically associated with the Jewish passover, but the precise details of this association are not clear. According to the synoptic gospels, Jesus’ last supper was a passover meal, which would place his death on the day after passover, while according to John his death occurred on the day itself, indeed at the very hour, when the paschal lambs were sacrificed. By the end of the 2nd century some churches celebrated Easter/Pascha on the day of the Jewish passover, regardless of the day of the week, while others celebrated it on the following Sunday. By the 4th century, the former practice had been abandoned practically universally, but differences still remained in the calculation of the date of Easter/Pascha. The ecumenical council held at Nicea in 325 AD determined that Easter/Pascha should be celebrated on the Sunday following the first vernal full moon. Originally passover was celebrated on the first full moon after the March equinox, but in the 3rd century the day of the feast came to be calculated by some Jewish communities without reference to the equinox, thus causing passover to be celebrated twice in some solar years. Nicea tried to avoid this by linking the principles for the dating of Easter/Pascha to the norms for the calculation of passover during Jesus’ lifetime.

8. While certain differences in the mechanics of determining the date of Easter/Pascha remained even after Nicea, which occasionally resulted in local differences, by the 6th century the mode of calculation based on the studies of Alexandrian astronomers and scholars had gained universal acceptance. By the 16th century, however, the discrepancy between this mode of calculation and the observed astronomical data was becoming evident. This led to the calendar change introduced by Pope Gregory XIII in 1582. Since that time, western Christians have come to calculate the date of Easter on the basis of this newer Gregorian calendar, while the eastern churches generally have continued to follow the older Julian calendar. While calendrical changes in some of the Orthodox churches in 1923 affected fixed-date feasts, the calculation of the Easter date remained linked to the Julian Calendar. Our present differences in calculation of the date of Easter thus may be ascribed to differences in the calendars and lunar tables employed rather than to differences in fundamental theological outlook.

9. In its study of the mechanics of the paschal calculation, the consultation took note of the fact that both the current eastern (Julian) and the current western (Gregorian) calculations diverge in certain respects from the astronomical data as determined by precise scientific calculation. As is well known, the Julian calendar at present diverges from the astronomical by thirteen days; the Gregorian at present does not diverge significantly, though it will in the distant future. Less well known is the fact that both Julian and Gregorian calculations rely upon conventional tables for determining the lunar cycle. For both modes of calculation, these tables at times give results that diverge from the astronomical data

The continuing relevance of the Council of Nicea

10. In the course of their deliberations, the participants in the consultation came to a deeper appreciation of the continuing relevance of the Council of Nicea for the present discussion. The decisions of this council, rooted as they are in scripture and tradition, came to be regarded as normative for the whole Church.

(a) Despite differences in the method of calculation, the principles of calculation in the churches of both East and West are based on the norms set forth at Nicea. This fact is of great significance. In the present divided situation, any decision by one church or group of churches to move away from these norms would only increase the difficulty of resolving outstanding differences.

(b) The Council of Nicea’s decisions are expressive of the desire for unity. The council’s aim was to establish principles, based upon the scriptural data concerning the association of the passion and resurrection of Christ with the passover, which would encourage a single annual observance of Easter/Pascha by all the churches. By fostering unity in this way, the council also demonstrated its concern for the mission of the church in the world. The council was aware that disunity in such a central matter was a cause of scandal.

(c) The Nicene norms affirm the intimate connection between the biblical passover (cf. especially Exod. 12:18, Lev. 23:5, Num. 28:16, Deut. 16:1-2) and the Christian celebration of “Christ our paschal lamb” (1 Cor. 5:7). While the council rejected the principle of dependence on contemporary Jewish reckoning, it did so on the grounds that this had changed and become inaccurate, not because it regarded this connection as unimportant.

(d) In the course of their discussions the consultation also gained a deeper appreciation for the wealth of symbolism which the Nicene norms permit. In the worship of many of the churches, especially in the biblical readings and hymnography of the paschal season, Christians are reminded not only of the important link between the passover and the Christian Easter/Pascha but also of other aspects of salvation history. For example, they are reminded that in Christ’s resurrection all creation is renewed. Some early Christian sources thus linked the Genesis account of the seven days of creation with the week of Christ’s passion, death and resurrection.

(e) The Council of Nicea also has an enduring lesson for Christians today in its willingness make use of contemporary science in calculating the date of Easter. While the council sought to advance the concrete unity of the churches, it did not itself undertake a detailed regulation of the Easter calculation. Instead it expected the churches to employ the most exact science of the day for calculating the necessary astronomical data (the March equinox and the full moon).

II. Two recommendations

First recommendation

11. In the estimation of this consultation, the most likely way to succeed in achieving a common date for Easter in our own day would be

(a) to maintain the Nicene norms (that Easter should fall on the Sunday following the first vernal full moon), and

(b) to calculate the astronomical data (the vernal equinox and the full moon) by the most accurate possible scientific means,

(c) using as the basis for reckoning the meridian of Jerusalem, the place of Christ’s death and resurrection.

12. This recommendation is made for the following reasons.

In regard to point a:

(i) The Church needs to be reminded of its origins, including the close link between the biblical passover and the passion and resurrection of Jesus Christ – a link that reflects the total flow of salvation history. In the estimation of this consultation, a fixed date would obscure and weaken this link by eliminating any reference to the biblical norms for the calculation of the passover.

(ii) Easter/Pascha has a cosmic dimension. Through Christ’s resurrection, the sun, the moon, and all the elements are restored to their primordial capacity for declaring God’s glory (Ps. 19:1-2, 148:3). Easter/Pascha reveals the close link between creation and redemption, as inseparable aspects of God’s revelation. The Nicene principles for calculating the date of Easter/Pascha, based as they are on the cycles of sun and moon, reflect this cosmic dimension much more fully than a fixed-date system.

(iii) In addition to underscoring many important symbolic aspects of the feast, a movable date for the observance of Easter/Pascha also indicates in palpable fashion the dramatic way in which the resurrection breaks into the comfortable routines of this world. While such a date may in some respects be less convenient than a fixed Sunday, it does call attention to a significant theological point which otherwise might be overlooked.

(iv) An earlier WCC consultation on the date of Easter/Pascha (Chambésy, 1970) observed, “In any case the churches should arrive at a solution for reasons based entirely on the religious meaning of the feast and for the purpose of Christian unity rather than for the purpose of satisfying inherently secular interests.” The present consultation wholly concurs with this sentiment.

(v) This recommendation maintains what, for most churches, is an important aspect of tradition. Adoption of a fixed Sunday approach would raise difficulties for many churches and, if introduced unilaterally by one church or group of churches, might well result in not two but three different dates for Easter/Pascha in a given year.

In regard to point b:

In recommending calculation of the astronomical data by the most accurate possible scientific means (as distinct, for example, from reliance on conventional cyclical tables or personal observation), the consultation believes that it is being completely faithful to the spirit of the Council of Nicea itself, which also was willing to make use of the best available scientific knowledge. We are fortunate that experts in astronomy have already provided these necessary calculations; they are conveniently presented in Synodica V (Chambésy – Genêve, Les Editions du Centre Orthodoxe, 1981) 133 – 149.

In regard to point c:

Astronomical observations, of course, depend upon the position on earth which is taken as the point of reference. This consultation believes that it is appropriate to employ the meridian of Jerusalem, the site of Christ’s passion and resurrection, as this necessary point of reference for the calculation of the March equinox and the subsequent full moon.

13. The recommendation just stated will have some different implications for the churches of East and West as they seek a renewed faithfulness to Nicea. Both will face the need for education of their faithful. For eastern churches, changes in the actual dating of Easter/Pascha will be more perceptible than for the western churches. Given the contexts in which these churches live, this will require both patience and tact. For western churches, on the other hand, the challenge may lie in communicating deeper aspects of the Nicene principles for the calculation of Easter/Pascha, such as those sketched above, and in acquainting their faithful with the concerns and insights of the eastern churches.

14. The consultation is well aware of the particular circumstances of many eastern churches. In some countries in the Middle East and Eastern Europe, where the Christian churches have lived with the challenge of other religions or materialistic ideologies, loyalty to the “old calendar” has been a symbol of the churches’ desire to maintain their integrity and their freedom from the hostile forces of this world. Clearly in such situations implementation of any change in the calculation of Easter/Pascha will have to proceed carefully and with great pastoral sensitivity.

15. To aid the churches in their discussion of the above recommendation, the consultation appends to this report a table of Easter/Pascha dates from 2001 through 2025, based on the astronomical specifications already indicated. For convenience of reference, the table also indicates the dates of Easter/Pascha according to the current Gregorian and Julian reckonings, the astronomically determined date of the first vernal full moon, i.e., the first full moon following the March equinox (cf. Exod. 12:18, Lev. 23:5, Num. 28:16, Deut. 16:1-2), and the date of passover according to current Jewish reckoning.

Second recommendation

16. This consultation also recommends that the churches now undertake a period of study and reflection towards the goal of establishing as soon as possible a common date for Easter/Pascha along the lines set forth above. In the year 2001 the paschal calculations now in use by our churches will coincide. Together, Christians will begin a new century, a new millennium, with new opportunities to witness to the resurrection of Christ and to proclaim their joy in his victory over sin, suffering and death. The unity that will be reflected as Christians celebrate Easter/Pascha on the same date will be for many a sign of hope and of witness to the world. This celebration of Easter/Pascha on the same date should not be the exception but the rule.

17. The way is now open for the churches to consider again their current practice for determining the date of Easter/Pascha. As a first step, in the interval between 1997 and 2001, this consultation encourages the churches to take up consideration of the recommendations here proposed, and, if they find them acceptable in principle, to explore ways of implementing them according to their own procedures, in light of their own opportunities, and within their own contexts. This consultation suggests that during these years the churches consult with each other on the ways in which a common date for Easter/Pascha can be implemented. In this interval also, the present consultation encourages continuation of existing local and regional initiatives, as interim measures, for observance of a common Easter/Pascha.

18. As a second step, the consultation suggests that the year 2001 would also provide a good opportunity for the churches to review reactions and to assess progress made towards agreement on this matter. It recommends, therefore, that the World Council of Churches, in cooperation with its ecumenical partners and other Christian groups, organize then a consultation in which this assessment could be reported and implementation could be discussed.

19. It is the sincere hope of the participants in this consultation that the churches will give an early and prayerful consideration to the recommendations made in this report, as a step towards preparing for a united witness to the death and resurrection of Jesus Christ.


Dr Bert Beach, U.S.A.
     (for the General Conference of the Seventh-day Adventists)
Metropolitan Damaskinos (Papandreou), Switzerland
     (for the Ecumenical Patriarchate)
Canon John Halliburton, United Kingdom
     (for the Anglican Communion)
Rev. Fayiz Y. Henain, Syria
     (for the Evangelical Churches in the Middle East)
Fr. Datev Mikaelian, Syria
     (for the Armenian Orthodox Church)
Archbishop Boutros Marayati, Syria (Armenian Catholic Church)
     (for the Middle East Council of Churches)
Ven. Dr. Koenraad Ouwens, Netherlands
     (for the Old-Catholic Churches of the Union of Utrecht)
Msgr. John Radano, Vatican City
     (for the Pontifical Council for Promoting Christian Unity)
Mr. Alexander Sologoub, Syria
     (for the Patriarchate of Moscow)
Archbishop Dr. Gunnar Weman, Sweden
     (for the Lutheran World Federation)
Metropolitan Elias Yusef, Syria
     (for the Greek Orthodox Patriarchate of Antioch)


Metropolitan Gregorios Yohanna Ibrahim
     (Syrian Orthodox Church of Antioch)
Mr Razek Syriani
     (Syrian Orthodox Church / MECC)


Prof. John H. Erickson, U.S.A.
     (Orthodox Church in America)
Rev. Dr. Ronald Kydd, Canada
     (Pentecostal Assemblies of Canada)

WCC Staff:

Fr. Dr. Thomas FitzGerald
     (Ecumenical Patriarchate)
Rev. Dr. Dagmar Heller
     (Evangelical Church of Germany, United)

Table for finding Easter/Pascha dates

         Easter/Pascha Easter/Pascha  Easter/Pascha  Vernal full  Passover by
 Year         by         by current    by current      moon by      current
         astronomical    Gregorian       Julian      astronomical    Jewish
           reckoning     reckoning      reckoning     reckoning    reckoning

 2001    15 April       15 April      15 April        8 April       8 April
 2002    31 March       31 March       5 May         28 March      28 March
 2003    20 April       20 April      27 April       16 April      17 April
 2004    11 April       11 April      11 April        5 April       6 April
 2005    27 March       27 March       1 May         25 March      24 April
 2006    16 April       16 April      23 April       13 April      13 April
 2007     8 April        8 April       8 April        2 April       3 April
 2008    23 March       23 March      27 April       21 March      20 April
 2009    12 April       12 April      19 April        9 April       9 April
 2010     4 April        4 April       4 April       30 March      30 March
 2011    24 April       24 April      24 April       18 April      19 April
 2012     8 April        8 April      15 April        6 April       7 April
 2013    31 March       31 March       5 May         27 March      26 March
 2014    20 April       20 April      20 April       15 April      15 April
 2015     5 April        5 April      12 April        4 April       4 April
 2016    27 March       27 March       1 May         23 March      23 April
 2017    16 April       16 April      16 April       11 April      11 April
 2018     1 April        1 April       8 April       31 March      31 March
 2019    24 March       21 April      28 April       21 March      20 April
 2020    12 April       12 April      19 April        8 April       9 April
 2021     4 April        4 April       2 May         28 March      28 March
 2022    17 April       17 April      24 April       16 April      16 April
 2023     9 April        9 April      16 April        6 April       6 April
 2024    31 March       31 March       5 May         25 March      23 April
 2025    20 April       20 April      20 May         13 April      13 April

For further information about this text, its availability in printed form
and in languages other than English, please contact Rev. Dr. Dagmar Heller

13 Responses to “On calculating Easter”

  1. asimplesinner Says:


    Helps explain why easter for Easterners will not always just be two weeks behind…

  2. asimplesinner Says:

    Woops! I put that in the wrong combox! I was sending the link to an Irish priest who noted that Eastern easter is just 2 weeks after Western because of the Julian… Not entirely accurate. (No coffee yet – sorry!)

  3. […] Easter and when it falls in the year. Something has to give before […]

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  5. Susan Peterson Says:

    How does this relate to the difference between Old Calendar and New Calendar Orthodox> I thought the difference between them was the difference between the Julian and Gregorian Calendars. But here you are saying that all Orthodox use the Julian calendar to calculate the date of Easter-because they first use it to calculate the date of the vernal equinox. Is there a difference between Old Calendar and New Calendary Orthodox Easter?

    It was very nice last year when my Orthodox son was able to call me up on Easter and say “Christ is Risen!” as his greeting, on the same day it was true for me. I am all for our having a common date.

    I think we should determine who would be most upset by changing the date they already use, and then use that one. Wouldn’t that be St. Paul’s formula for resolving such issues?

    Susan Peterson

  6. Susan Peterson Says:

    I think you already answered my question, on reading further. Sorry. SFP

  7. bekkos Says:

    Dear Susan,

    Unfortunately, I don’t see how one could objectively determine who would be most upset by changing the date, since there would be hard feelings either way, and fanatics could easily compete with one another in respect of proclaiming their hurt feelings. It seems to me that the recommendations of the Middle East Council of Churches make more sense: keep to the Nicene norms and calculate the astronomical data according to the best scientific reasoning. Otherwise, I don’t really see how one escapes the criticism of St. Paul, Gal 4:10, “Ye observe days, and months, and times, and years.” That is to say, when people make matters of calendar part of the essence of the faith, how are they not subordinating the one faith of Christ to the “beggarly elements” of this world?


  8. bekkos Says:

    It was recently pointed out to me that my comments, at the beginning of this posting, which ascribe the differences in the dates of Easter to the calendar alone, are a little too simple. Last week Prof. William Tighe forwarded to me a letter to him from Mr. Graham Hutton. Below are Mr. Hutton’s letter, and my reply to it.

    * * *


    Thank you for this. It is very interesting, but there seems to be something more to it than the explanation given in the article. If the difference between Orthodox and Catholic Easter were simply a matter of when the vernal equinox falls this would mean that in years where a full moon were to occur between March 21st and April 3rd the Orthodox and Catholic Easters would differ but that in years where there no full moon were to occur between these dates the Churches would share the same Easter since they would both identify the same full moon as the vernal full moon. From the table one can see that this is indeed often the case (such as in 2001, 2004 and 2007) when the vernal full moon falls on 15th, 11th and 8th April respectively and both Churches have the same date for Easter. However it seems not to be invariably the case: in 2009, for example, the vernal full moon is on 9th April and the Catholic Church will celebrate Easter on the following Sunday (12th April) yet the Orthodox, it would seem, will wait another week until 19th April. The same odd phenomenon occurs in 2012 and 2015.

    Even stranger is the fact that in 2010 when the vernal full moon is on 30th March (ie this should not be the vernal full moon for the Orthodox since it comes before 3rd April) both Churches keep Easter on 4th April.

    As far as I can see the Catholic calculation is always consistent with the rule but it would seem that there is another factor at play for the Orthodox.

    I would also be fascinated to know what happened in England before the Gregorian calendar was adopted. Was Easter observed here according to the Julian calendar which, if what I have noted above is correct, could have been yet a third date coinciding with neither the Catholic or Orthodox Easters.


    * * *

    Dear Mr. Hutton,

    Prof. William Teague forwarded to me the other day your reply to him regarding my article “On calculating Easter” …. I see your point; if the thirteen-day difference between the Gregorian and the Julian dates for the vernal equinox were the only significant factor affecting differences in Easter date, then Easter in years like 2009, 2012, and 2015 should occur on a common day, since, in those three years, the vernal full moon follows April 3rd, the Julian date for the equinox; the “first Sunday after the first full moon after the vernal equinox” should accordingly be the same day for everyone on those three years, yet, in fact, it is not. You conclude from this that there is some other factor at play for the Orthodox.

    The other factor, I think, is mentioned in §9 of the article I posted from the World Council of Churches and Middle East Council of Churches Consultation. The document there states:

    “As is well known, the Julian calendar at present diverges from the astronomical by thirteen days; the Gregorian at present does not diverge significantly, though it will in the distant future. Less well known is the fact that both Julian and Gregorian calculations rely upon conventional tables for determining the lunar cycle. For both modes of calculation, these tables at times give results that diverge from the astronomical data.”

    Apparently, the reason why the formula “the first Sunday after the first full moon after the vernal equinox” yields different dates in years like 2009, 2012, and 2015, when the difference in calculating the vernal equinox is no longer a factor, is that the lunar calculations on those years also differ significantly. For instance, although the astronomical vernal full moon occurs next year on April 9th, apparently the Julian lunar tables, relied upon by the Orthodox Church in calculating the date of Easter, predict a full moon for after (the Gregorian) April 12th, the date of Western Easter that year; for this reason, the Orthodox won’t celebrate Easter next year until a week later.

    This raises some interesting questions. Where are these “conventional tables for determining the lunar cycle” to be found? When were they drawn up? What astronomical theories and evidence do they rely upon? And who, effectively, does the determining?

    In the fourth and fifth centuries, the see of Alexandria had some responsibility for announcing to other churches the correct Easter date; cf. Nicene and Post-Nicene Fathers, ser. 2, vol. 4, p. 500: “The variations of practice which had rendered the Paschal Feast a subject of controversy from very early times … had given rise to the custom of the announcement of Easter at a convenient interval beforehand by circular letters. In the third century the Bishops of Alexandria issued such letters (e.g. Dionysius in Eusebius, Historia Ecclesiastica vii.20), and at the Council of Nicaea, where the Easter question was dealt with, … the Alexandrian see was requested to undertake the duty of announcing the correct date to the principal foreign Churches as well as to its own suffragan sees…. This was probably due to the astronomical learning for which Alexandria was famous.” One might ask: Does anyone, in the Orthodox Church, have a similar function at the present time, of officially determining what is the correct date of Easter?

    In fourteenth-century Byzantium, there was a revival of the study of astronomy among men like Theodore Meliteniotes and Nikephoros Gregoras; the latter, in 1325, proposed a revision of the calendar, similar to what was later adopted by Pope Gregory XIII. The Emperor Andronikos II decided not to implement it, in part it seems because he feared it would stir up troubles between Byzantium and its Orthodox neighbors, who would not easily be persuaded to change anything, and who might take a calendar reform as grounds for questioning the Greeks’ Orthodoxy. (See Krumbacher, Geschichte der byzantinischen Litteratur, 2nd ed. [Münich, 1897], pp. 293 f.) Perhaps Andronikos saw a similar danger of division among the Greeks themselves. The background to Gregoras’s failed calendar reform is, no doubt, the mutual dislike that existed in late Byzantium between humanist scholars and hesychast monks; the Gregoras who had advocated revising the calendar to accord more closely with astronomical phenomena was the same Gregoras who later became one of St. Gregory Palamas’s principal opponents….

    So, although it is true, in a general way, to say that the difference in the dating of Easter is due to the difference between the Julian and the Gregorian calendars, you are quite right to point out that this difference between the calendars is not simply a matter of a thirteen-day shift in reckoning the date of the vernal equinox. There are also standard tables for calculating the full moon that accompany these two calendars, which differ in important ways. Where these tables may be found, what evidence they are based upon, and what methods and scientific theories they assume in making their calculations, are all questions for which I have no immediate answer. I am very grateful to you for bringing this issue to my attention.

    Yours truly,
    Peter Gilbert

  9. bekkos Says:

    For anyone still interested in investigating the Easter-date question, I found today an excellent article on the subject, in the Two Natures blog:


  10. Would I show my hand as a knuckle-dragging trogladyte if I were to reveal that – as things stand right now – I am not terribly bothered that there are often two celebrations of Christ’s death and resurrection in a year?

  11. bekkos Says:

    Probably not. Nor was it my intention in posting this article that you should be considered so. But some people did wonder this year why the celebrations of the Paschal feast occurred so far apart, which raised the question of why they occur at different times at all. That is why I posted the WCC article, and it is what most of the comments in the subsequent thread have aimed at clarifying.

    I do think, however, that a common date for celebrating the Easter feast is, in and of itself, a desirable thing, and that the lack of such a common celebration is a particularly glaring and unnecessary sign of Christian disunity. In some cases, I think the reasons advanced for not keeping a common date suggest a worshipping of the calendar, an “observing of times” such as St. Paul warns against. But you may be right that, in an age where secular holidays are routinely moved to Mondays or Fridays to make for long weekends, and where even major religious feasts are moved by some churches to Sundays in observance of the principle of utility, a discussion over keeping a common date for Easter may seem to lack urgency. I would submit that apathy over the issue is more a matter of minds being dulled to religious symbolism than it is due to any unimportance of the question itself.

    (P.S. The word is spelled “troglodyte.” Just for future reference.)

  12. “(P.S. The word is spelled “troglodyte.” Just for future reference.)”

    You must not be one of my 8 faithful readers. Were it the case that you were, you would know my typos are legendary and beyond all hope.

    Sorry, Sr. Margaret Ann, SND, wherever you are.

  13. ben mann Says:

    just came across this…


    Patronal Feast Day at the Monastery of the Sacred and Life-giving Calendar!

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