Easter dates and Calendars

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Why do the dates for Pascha/Easter often differ between the Orthodox Chuch and the Western Church? Last year, Pascha (Easter Sunday) fell on exactly the same day for the Orthodox Church and the Western Church. It will be the same again in the years 2017, 2025, 2028, and more, but different for all the other years in between. How can this be when all Christian churches are celebrating the one and only resurrection from the dead of our Lord Jesus Christ nearly 2000 years ago? This article is an attempt to explain why there are these differences between Eastern and Western Christian date counting practices, particularly when it comes to Easter.



According to the New Testament, Christ was crucified on the eve of the Jewish Passover (See John 19:14) and then shortly afterwards He rose from the dead. Because of this, the Christians have always commemorated Christ’s resurrection around the time of the Jewish Passover. But, from the earliest days, there were differences in exactly how this was done.

At the very beginning of the Church’s history, Christians of Jewish origin celebrated the resurrection of Jesus Christ immediately following the Jewish Passover festival, which, according to their Babylonian lunar calendar, fell on the evening of the full moon (which was the 14th day in the month of Nisan, the first month of the Jewish year — see Leviticus 23:5). By their reckoning, Pascha fell on the same date every year, but different days of the week (This is the same as it is for Christians today celebrating Christmas; it is always celebrated on December 25th, regardless of which day of the week it falls on).

Christians of Gentile origin, descendants of the Greco-Roman civilisation, however, wished to always commemorate the resurrection of Jesus Christ on a Sunday, the day of the original resurrection and the first day of the week. According to their method, Pascha occurred on the same day of the week every year, always a Sunday, but from year to year it fell on different dates (Like today).

These different methods continued alongside one another in the Christian world until 325AD when Emperor Constantine I called together the First Ecumenical Council of Nicaea. One of the decisions made by the Council was that all Christians should celebrate Pascha on a common day. It was decided that Easter should be celebrated throughout the Christian world “on the first Sunday after the full moon following the vernal equinox.” (An equinox is a day on which the sun crosses the equator, approximately March 21st and September 22nd, when day and night are of equal length everywhere. Vernal is from the Latin for spring so the vernal equinox refers to the March date of the equinox in the northern hemisphere. It is sometimes referred to as the March equinox). It was also stated that should the full moon fall on a Sunday, thereby coinciding with the Jewish Passover festival, Easter Sunday would be delayed until the following Sunday. In this way it was planned that the feasts of Christian Pascha and Jewish Passover would never coincide.

Unfortunately, the Council of Nicaea made few decisions that were of practical use as guidelines for the calculation of Easter Sunday, and it took several centuries before a common method was accepted throughout Christianity. Because of the limitations in astronomical knowledge in the fourth century it proved to be an impossible task to accurately determine the correct date according to the Council’s instructions (The exact orbit of the moon was not known precisely until recent times). The main problem facing the church in its calculations was a gradually increasing gap between the true astronomical year and the Julian calendar in use at the time.

The Julian calendar is a solar calendar in which the day is determined by the rotation of the earth with respect to the direction of the sun, and the year is determined by the rotation of the earth around the sun. (Not all calendars are based on the sun. For example the Muslim calendar is moon-based, whilst the Babylonians based their calendar on a combination of the sun and moon). The Julian calendar was named after Emperor Julius Caesar who introduced it in 45 BC as the calendar for the Roman Empire. It was quite accurate for its time, but was in fact 11 minutes and 14 seconds longer than the actual solar year. This meant that the Julian calendar year developed a gap between itself and the true astronomical calendar of one day for every 128 years.

Because of these problems the Church devised a method for the calculation of Easter that did not depend on astronomical accuracy. The idea was that the date of Easter could be worked out without astronomical knowledge. The Church decided to define Easter with respect to an imaginary moon - known as the Ecclesiastic Moon. Also the date of the equinox was fixed at March 21st, even though it can vary slightly from this date. With this definition the date of Easter can be determined in advance without further astronomical knowledge.

Even this method was not without problems, sometimes resulting in Easter being celebrated at different times in different parts of the world. In 387AD for example, the dates of Easter in France and Egypt were 35 days apart!

In its attempt to find a solution to these problems, in 465AD the church adopted another system of calculation proposed by the astronomer Victorinus, who had been commissioned by Pope Hilarius (Pope from 461-468AD) to reform the calendar and fix the date of Easter. Elements of his method are still in use today. Refusal of the British and Celtic Christian churches to adopt the proposed changes led to a bitter dispute between them and Rome in the 7th century. Disagreements about the date of Easter are nothing new!

The Gregorian calendar

The new system however, did not eliminate the ever-growing gap between the Julian calendar and the true astrological year caused by the addition of an extra 11 minutes and 14 seconds each year. By 1582 the actual vernal equinox occurred 10 days before it appeared in the calendar! If allowed to continue for long enough, Christmas would eventually occur at the same time as the northern hemisphere Harvest Festival! This potential calamity led Pope Gregory XIII (1502-1585) to appointed a committee, which managed to reduce the error to 26 seconds per year or one day in about 3,323 years. To correct the already existing gap, Pope Gregory also issued a decree dropping 10 days from the calendar. The result was that the Julian calendar date of Thursday October 4th 1582, was followed the next day by the Gregorian calendar date of Friday October 15th 1582, thus removing the 10 dates, October 5th to 14th inclusive.

The Gregorian calendar was then slowly adopted throughout Europe. France and the Catholic parts of Germany, Switzerland, and the Netherlands immediately complied. Poland adopted the Gregorian calendar in 1586, and Hungary in 1587. The Protestant parts of Germany, Switzerland, and the Netherlands did not change until 1700. Great Britain and the colonies did not change until 1752, by which time they needed to make an adjustment of 11 days. (So when the British explorer and navigator, who discovered Australia, Captain James Cook, was born in 1728 the British Empire was still using the old Julian calendar). The British, who have always been very conservative in nature, actually rioted in the streets of London over the loss of September the 3rd to 13th inclusive that year! Sweden changed over in 1753, Japan in 1873, China in 1912, Turkey in 1917, Soviet Russia in 1918 and Rumania in 1919. In May 1923 Greece became the final country to accept the Gregorian calendar. Easter day has been celebrated on the same day throughout the non-Orthodox world and some other parts ever since.

In the Orthodox world however, even though the some of the civil authorities had adopted the Gregorian calendar, the church often did not. And this has led to the situation we find ourselves with today.

Many people ask why the Russian Orthodox Church celebrates Christmas on January 7th. These same people may also wonder why Russia celebrates the “October Revolution” on November 7th, and the answers to both questions are related. At the time the communists seized power in Russia, the country was still using the Julian calendar. It was only after the Communists seized power, that Russia adopted the Gregorian calendar as its civil Calendar. But since the October Revolution happened before this change, they ended up with a revolution that had occurred on October 25th on the Julian calendar being celebrated by the Soviets on November 7th on the Gregorian calendar! Likewise, though the Russian Church celebrates Christmas on December 25th on the Julian calendar, this happens to fall on January 7th on the Gregorian calendar.

At the present time only the Russian, Georgian, Jerusalem, and Serbian Orthodox Churches and Mount Athos monasteries are living according to the “Old” (Julian) calendar. All other 11 Orthodox Churches celebrate Christ’s Nativity on December 25th as the Western Church does, using the Gregorian calendar. All Christians actually celebrate Christmas on the 25th December! However on different calendars! So the Russians celebrate on 25th December using the “Old” Julian calendar, which is actually January 7th at the moment on the Gregorian calendar!

There was an attempt by the Soviet government to force the Russian Orthodox Church to accept the “New” calendar, but this attempt failed. The adherence to the “Old” Calendar became a powerful symbol of resistance to the Communist goal of destroying the Church. As a result, the Russian Church has continued to use the “Old” Julian calendar to this day, even after the communist threat has passed.

The Revised Julian calendar

In 1923 the Greek Orthodox Church held a “pan-Orthodox” synod (less than a general synod, but more than a local one) that revised the “Old” Julian calendar to what is now known as the “Revised Julian Calendar” (something very close to the Gregorian, although the formula is slightly different). This was done for the same reasons that the Gregorian calendar had been developed by the Western Church - to correct for the ever-increasing gap between the “Old” Julian calendar and the true solar year.

The Revised Julian calendar average year length accumulates only one day of drift for each 31,034 years, so it is in fact more accurate than the Gregorian calendar. Within the years spanning 1600 to 2799, the Revised Julian and Gregorian calendars are exactly the same.

This Pan Orthodox Synod used a technicality to get around previous Orthodox condemnations of the Gregorian calendar, namely that of keeping the method of calculating the dating of Easter unchanged. So the Orthodox Churches continue to use the “Old” Julian Calendar’s Paschalion for the purposes of determining the date of Easter (Pascha) and this is why Orthodox Easter is usually at least a week after that of the Gregorian Calendar, and can be as much as a month later (as it will be this year). And here lies the key to understanding the different dates for Pascha that the Western and Eastern churches have for celebrating the same event, the one and only resurrection of Jesus Christ from the dead.

The clash in calendar dates

The next question is, if the two calendars are 13 days apart at the moment, how was it possible for the date to be the same last year (2004) and 34 days different this year (2005)?

It is a combination of things. The Orthodox Church uses the fixed date of 21 March in the Julian calendar in order to calculate the vernal equinox, while the Western church uses the fixed date of 21 March in the Gregorian calendar (The 21st of March in the “Old” Julian calendar is the equivalent of the 3rd of April in the Gregorian calendar until 2099, and then it becomes the 4th April from 2100).

Between 326 AD and 1582 AD Easter Sunday dates were based on the Julian calendar in use at that time. Pascha Sunday was defined as the Sunday following the Paschal Full Moon date for the year, using a simple “19 Paschal Full Moon dates” table of the “Old” Julian calendar. This was replaced in the Western Church in 1583 AD by a new larger (revised) “Paschal Full Moon Gregorian dates” table. The Eastern Church continues to use the 19 Paschal Full Moon dates table.

So the current Easter calculations of Eastern and Western Churches use differing cycles of Ecclesiastical Full Moon dates and different tables, so we should not be surprised that the results frequently turn out differently.

In some years the Orthodox Easter Sunday does occur on the same day as the Western Easter Sunday. For example, this occurred in 2004 because the Western Easter Sunday date of April 11th, 2004 (Gregorian calendar) was the same day as the Orthodox Easter Sunday date of March 29th, 2004 (“Old” Julian calendar). In most years however, Orthodox Easter follows Western Easter by one or more weeks, but for some years there are wider gaps. Year by year, Orthodox Pascha moves back and forth between its earliest date on April 4th and its latest date on May 8th - as set by the rule of the Council of Nicaea in 325AD using the “Old” Julian Calendar. The Western Easter also moves back and forth, between its earliest date of March 22nd and its latest date of April 25th, but the two movements are not always together. There is an unusually wide gap this year, because the Western Easter falls at an early date in its cycle, while the Orthodox date falls late in its cycle.

The problem is not just between the Western and Eastern Churches. There are also variations within both Churches. Within the Orthodox Church for example, we find that the Orthodox Church of Finland keeps Pascha according to the Gregorian Calendar because they were forced to do so by the Finnish government. There are some Orthodox churches on the “New” Revised Julian calendar and some on the “Old” one. On the other hand, within the Western Church there are some Eastern Roman Catholics (Ukrainian, Russian, Lebanese, etc.) who use the “Old” Julian calendar. The Pope allows them to celebrate Christmas on 7th January for example, along with the “Old” calendar Orthodox. He also allows his Melkite Catholics to celebrate Easter with the Orthodox and not with the Roman Catholic calendar!

These are problems that may take some time for the Church as whole to resolve. Hopefully there will be some agreement before the difference between the two calendars increases from 13 days to 14 (in 2100)!

So, the Church is currently passing through one of those times in history when it is very much in need of another Ecumenical Council to sort out the variations that have occurred as a result of historical, political and astronomical developments over the centuries since Christ"s resurrection.

In 1968 the Patriarch of Constantinople suggested to Pope John the 23rd that the day of celebration be unified. Agreement was reached between them but more time was asked for the faithful to prepare for the changes. We await progress.

In the meantime, what should our attitude be to others who celebrate Pascha at a different time to us?

Avoid arguments about the dates of Pascha. The enemy of our souls loves to make us fight over things like this and to distract us from the most important issue. The most important issue is our faith in the risen Christ, not dates and times of celebrations which are beyond our control.

One of our early church Fathers gave us this phrase to meditate on, “IN NECESSARIIS UNITAS, IN DUBIIS, LIBERTAS, IN OMNIBUS CARITAS,” which is Latin for:

In necessary things, unity; in dubious things, liberty; in all things, love.

All Christians are united in their desire to commemorate the resurrection of Jesus Christ from the dead. Until the Church can sort out the variations that have arisen over the centuries we must show love to one another, while praying for the day when there will be a common celebration for all Christians and a united witness to those outside the Church.


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Learn more about what Pascha celebrates.