This post was written by my father, John Weaver, and originally published on September 18, 2015 on his blog: beorminga.wordpress.com. I am preserving them on my website as his blog posts are remarkable in their thoroughness and depth of research. Enjoy!

Dates of Easter, Pascha and Passover

Whenever the Eastern Orthodox Church celebrates Easter one or several weeks after the Western Easter, the inevitable questions arise as to why this is so.  Some of the responses I have heard over the years simply didn’t ring true and even on official-looking web sites I have seen statements that confuse rather than clarify the issue — such assertions as “the Eastern Church sets the date of Easter according to the actual astronomical full moon” (not true), “the Eastern Orthodox Church also applies the formula so that Easter always falls after Passover” (meaningless), “Orthodox Easter is always celebrated the Sunday after the Jewish Passover” (wrong),  “the rule set forth by the First Ecumenical Council … requires that Pascha must take place after the Jewish Passover in order to maintain the Biblical sequence of Christ’s Passion” (a redundant ‘rule’ on the Julian calendar for which there is no evidence).

In 2012 I wrote the following piece in an attempt to clarify the confusion about Easter dates in my own mind and I have passed it on to a few people who have asked for an explanation of how the dates are determined.  Before posting it here I have added a couple of new references including one to a very recent (March 2015) blog which supports much of what I have written.

Easter, Pascha and Passover

Most people are aware of the Julian and Gregorian calendars and know that most Orthodox churches use the former while the rest of Christendom follows the latter. They may not be as familiar, however, with the rules for determining the dates of Easter (or Pascha in the Orthodox Church) and why they are usually, but not always, different on the two calendars. Before delving into these differences let us remind ourselves of the historical origins of the two calendars.

In an attempt to coordinate the days of the year with the orbit of Earth about the sun, the Julian calendar was authorised by Julius Caesar in 46 BC as a replacement for the rather haphazard Roman calendar that had been used hitherto. The new calendar was based on the best advice available from astronomers at that time. It comprised a year of 365 days with the added proviso that every fourth year, what we now call a leap year, would include an additional day in order to keep the calendar in line with Earth’s orbital period and hence with the seasons as well. All went well for a few hundred years but by the 16^th century it was clear that the equinoxes (when the sun is directly over the equator) were slipping backwards relative to the calendar. This was of particular concern to the Roman Church because the date of Easter was supposed to be determined by the vernal (or spring) equinox in the Northern hemisphere which was arriving ever earlier in the calendar year. In fact all Christian feast days were no longer synchronised with the seasons; Christmas was drifting towards spring and Easter was heading inexorably into the summer. In other words, it was realised that the actual solar year, the time it takes Earth to complete its orbit around the sun, was slightly shorter than the Julian calendar year introduced back in 46 BC.

Although this discrepancy was only a few minutes, over the centuries it had accumulated into several days. In order to correct this error, Pope Gregory XIII accepted a recommendation for calendar reform from a Jesuit astronomer, Christopher Clavius. It involved a one-time omission of ten days from the calendar to compensate for the excess of days already accumulated on the Julian calendar, and thenceforth a refinement in how leap years were to be determined – the extra day would no longer be included in years divisible by 100, except for those that were also divisible by 400. For example, the year 1900, although divisible by 4 and therefore considered a leap year in the Julian calendar, was not a leap year on the Gregorian calendar. On the other hand, the year 2000 was a leap year on both calendars because it is divisible by 400. Thus, on the Gregorian calendar Russian Orthodox Christmas was on the 6^th of January in the 19^th century, and will shift to the 8^th of January after 2100, but it remained fixed on the 7^thof January at the last millennium.

The new Gregorian calendar was implemented by Roman Catholic countries but its acceptance elsewhere was spasmodic, possibly because it was viewed with some suspicion in certain quarters as a papist innovation. Great Britain did not adopt the Gregorian calendar until 1752; Russia introduced it as a civil calendar after the 1918 revolution; and it was not until 1923 that Greece made the change by which time they had to remove 13 days from their calendar year. Despite its Roman Catholic origins, the Gregorian calendar is now recognised by most countries as the universal civil calendar.

The Anglican, Lutheran and other churches have also long since accepted the new calendar and based their liturgy on it, but the Orthodox Church has remained steadfastly resistant to change. At a synod held in Constantinople in 1923, however, a proposal for a ‘Revised Julian Calendar’ was introduced. Despite its name, the Revised Julian calendar is virtually the same as the Gregorian calendar, differing only by a small refinement in the way leap years are calculated. In fact, up to the year 2800, which will not be a leap year on the Revised Julian calendar, the two calendars are identical. It was accepted by some Orthodox churches, notably the Greek Church, but rejected by others, notably the Russian Church. That is why, for example, the Greeks celebrate Christmas on the 25^th of December but the Russians on the 7^th of January.

At the same synod a revised method for calculating dates of Pascha was also recommended. It was based on exactly the same principles originally promulgated by the 1^st Council of Nicaea in the year 325, but expressed in a more precise form. Thus Pascha was stated to be the Sunday following the 24-hour day on the meridian passing through the Church of the Holy Sepulchre in Jerusalem during which the first full moon after the vernal equinox occurred, with the additional clarification that when the exact instant of full moon happened to fall on the same day as the instant of the equinox, the latter must precede the former (otherwise the next full moon would be the relevant ‘Paschal moon’). This would have removed the ambiguities present in the original definition but unfortunately there was no agreement among the various Orthodox churches to adopt this proposal and, with the exception of the Finnish and Estonian Orthodox churches (which have adopted the Gregorian calendar), they have continued to use the Julian calendar for determining the dates of Pascha.

Which brings us to the main theme of this discussion – how are the dates of Easter (Pascha) determined and what role, if any, does the date of the Jewish Passover play in their determination? In the Early Church, Easter was celebrated on various dates by different Christian communities. Some celebrated Easter on Passover itself whatever the day of the week, others on the Sunday following Passover, and yet others calculated an appropriate date for themselves. Moreover, those who were basing Easter on the rather erratic Jewish calendar at that time sometimes found that Passover occurred twice in the same year! The bishops assembled for the Council of Nicaea attempted (among the many other important decisions they made) to bring order to this chaos. Although precise minutes of their deliberations are apparently not recorded, the theme of their pronouncements on this topic emerges very clearly from a subsequent letter sent by Emperor Constantine to all those not present at the Council. First, all churches should celebrate Easter on the same day; second, this day should be a Sunday; and third (expressed by Constantine in very strong anti-Jewish rhetoric), Easter should be completely divorced from the Jewish calendar (see Documents from the First Council of Nicaea scanned from ‘The Seven Ecumenical Councils of the Undivided Church’, Vol. XIV, 1988, Henry R. Percival (ed.), which is also available on the Fordham University website).

The Council agreed that the date of Easter should be on the Sunday following the first full moon after the vernal equinox. Although this appears at first sight to be a unique date based solely on astronomical observations, it is in fact fraught with the ambiguities alluded to earlier. The vernal equinox is not always on the same day; it can occur on any of the five days from the 18^th to the 22^nd of March; the instant at which the full moon appears can have different dates at places on different longitudes. Even with the approximate time zones in modern usage, for example, a full moon at 12:30 a.m. on the 22^nd of March in Jerusalem is observed in Rome at 11:30 p.m. on the 21^st.

To overcome these difficulties, it was decided that for ecclesiastical purposes the vernal equinox would be deemed always to have occurred on the 20^th of March, and tables of the ‘ecclesiastical full moon’ were drawn up which likewise specified dates of the full moon in any year to be used for calculating the date of Easter. Although the ecclesiastical full moons were only approximations to the astronomical full moons, they were remarkably accurate considering how long ago they were calculated. Finally, the Paschal full moon was defined as the ecclesiastical full moon after the 20^th of March (the hypothetical equinox). Putting all this together, we can state an accurate definition of Easter and Pascha as follows:

Easter falls on the Sunday following the date of the Paschal full moon for that year

(R. W. Mallen, 2002, Easter Dating Method). Note that this definition faithfully follows the decisions taken by the 1^st Nicene Council, is equally applicable in both the Eastern and Western churches, and is not dependent on the date of Passover. Many writers claim that the Council specified the 21^stof March rather than the 20^th as the fixed date for the vernal equinox, in which case the definition of the Paschal full moon should be modified to read ‘the ecclesiastical full moon on or after the 21^st of March’.

The reason for the different dates of Easter and Pascha is now clear. Because the equinox was fixed to a calendar date rather than astronomical observations, the dates of Easter and Pascha started to diverge once the Western Church adopted the Gregorian calendar. The earliest possible date for Easter is the 22^nd of March, in a year when the Paschal full moon falls on a Saturday that also happens to be the 21^st of March. According to the Julian calendar, however, the 22^nd of March is presently the 4^th of April on the Gregorian (and civil) calendar. Thus Orthodox Pascha can never occur before the 4^th of April and as the centuries pass, this date will gradually drift ever away from spring, from Passover and from Western Easter. After the year 2698, Easter and Pascha will never again coincide. Another less dramatic factor affecting the computed dates, which is nevertheless the reason why a one-week separation of Easter from Pascha is fairly common (as in 2012, for example), is that when the Gregorian calendar was adopted the tables of Paschal full moons were also corrected. The Orthodox churches have retained the original tables which means that the tabulated Orthodox Paschal full moons are now occurring a few days later than the corresponding Gregorian Paschal full moons.

So what have all these determinations of Easter dates to do with the Passover? In my view, absolutely nothing! None of the algorithms and tables used to calculate the dates of Easter and Pascha require information about the date of Passover. I have been unable to find any evidence at all to support the statements regularly made by many Orthodox priests and believers that the 1^st Nicene Council demanded that Easter should always follow Passover. Rather the opposite; the intent of the Council was that Easter should in no way be linked to the Jewish calendar. Nicolas Ossorguine, an Orthodox theologian at St. Sergius Theological Institute in Paris writes:

The idea that the Christian Pascha must always be observed following the Hebrew Pesach was advanced by Byzantine canonists during the time preceding the introduction of the Gregorian calendar in the West (1583 AD). Apparently it was done in an attempt to discredit this forthcoming “Catholic” calendar reform.  

(See this translation by Alvian Smirensky in 2002 from the original article written in 1979). I think there is strong evidence to support this statement because the date of Pascha calculated on the Julian calendar will de factoalways follow Passover. To state it as an additional requirement is as redundant as saying Easter must follow Valentine’s Day!  It always does. The reference to Passover can only have been introduced in a negative sense in order to refute the validity of the Gregorian calendar which does occasionally allow Easter to precede Passover. More recently, Archbishop Peter of the Orthodox Church in America wrote in the 1994 April/May edition of The Orthodox Church Newspaper:

There is among the Orthodox a very widespread belief that the Christian celebration of Easter must necessarily come after the Jewish Passover. This chronological order is considered imperative and bears a symbolic meaning, as it is believed to have been decreed by the First Ecumenical Council … Yet, not only is such a stipulation totally absent from the decision taken on the Paschal question at Nicea, but it is foreign and, in a sense, contrary to what was then decreed. 

And in an interesting blog posted in 2015, Fr. Andrew Damick (an Orthodox priest) labels the rule that Pascha has to be after Passover as Urban Legend Number 1 tracing its origins to a rather casual observation by a 12^th century canonist.  It is remarkable that a rule based on such flimsy and unsubstantiated grounds can acquire the status of Church doctrine merely through constant repetition and unquestioning acceptance over many years.

I am certain that the immediate response from many Orthodox adherents will be “so what?”; Pascha must indeed always follow Passover in order to preserve the chronological order of events that took place 2000 years ago. Jesus rode into Jerusalem to celebrate the Passover and was crucified shortly thereafter. Consider, however, the dates of Easter and Pascha in 2013 when the vernal equinox occurred at 11:02 on the 20^th of March universal time and the next full moon was at 09:27 on the 27^th of March. Passover was on the 26^thof March and Gregorian Easter fell on the 31^st of March. It satisfied all the alleged criteria the Orthodox Church prescribes by occurring on the Sunday after the full moon after the vernal equinox and after Passover. Surely, then, 2013 must have been one of those years in which Easter and Pascha were coincident. But no, Pascha didn’t arrive until the 5^th of May, a full 5 weeks later!  How this represents a more accurate representation of the historical chronology of the Resurrection relative to Passover escapes me. The reason for the delay is, of course, that the earliest Pascha can occur has slipped to the 4^th of April as explained above and has nothing at all to do with the date of Passover. Indeed, if preservation of the order of the historical events is so paramount, why not revert to the practice of some early Christian groups by always celebrating Pascha on the Sunday following Passover? This would satisfy those who are adamant that Pascha must follow Passover, and would do so with historical accuracy according to the Jewish calendar, but that would then be completely counter to the directives of the 1^st Nicene Council.

On a previous occasion when a similar situation to that in 2013 arose, an Orthodox friend justified it by maintaining that it wasn’t just Passover itself but the full Passover week that must precede Pascha. That explanation can be put to rest immediately by considering the relevant dates in the year 2014, when Passover week ran from the 15^th to the 22^nd of April and Easter and Pascha were celebrated together during that very same week, on the 20^th of April.

A final argument in defence of the ‘Old Calendar’, which is sometimes used by devout Orthodox believers, is that it must be true because certain miraculous events such as the spontaneous combustion of the Holy Fire and the appearance of images in the sky always occur on Orthodox Pascha, not on the dates for Easter on the Gregorian calendar. For me, such claims merely diminish the credibility of the events rather than add authenticity to the Julian calendar. I cannot envisage a God that keeps track of man-made, ever-shifting and inaccurate dates that no longer represent the equinoxes in the Sun-Earth system that He created, in order to ensure that His miracles occur on the right day at a specified time. I recognise, however, that beliefs in such miraculous happenings are personal and emotional, and that no amount of rational persuasion will change them.

There are a number of web sites that provide automatic calculators of the dates of Easter, Pascha and Passover for any given year. One that is particularly user-friendly can be found here.  Interesting consequences arise if one looks forward several millennia. In the year 7010, some 5000 years from now, Passover will occur on the 19^th of April, Easter on the 22^nd of April and Orthodox Pascha on the 10^th of June, 52 days after Passover! And while Orthodox churches remaining entirely on the Julian calendar will experience Christmas and Pascha slipping in tandem relative to the seasons, those that have adopted the Revised Julian calendar for fixed feast days but not for Pascha will find Pascha gradually closing in on Christmas as the former advances into summer and autumn while the latter remains fixed. Eventually calendar reform will have to be adopted, and I hope when that time comes all Christian churches will settle on a fixed date for Easter (Pascha), perhaps on the second Sunday in April.

John Weaver