On 17 November 2011, at a meeting of the Catholic Patriarchs of the Orient in Lebanon, the bishops once again called on all Christians to agree on a single date for Easter. At present the Roman Catholic and Protestant churches calculate the date of Easter differently than the Orthodox churches. This results in both sets of Christian churches often having different dates for Easter. The bishops believed that all Christians celebrating Easter on the same day would be a sign of Christian unity.
When I was asked to write on this, I thought that there were some deep theological differences involved. Research into the topic made me realize that I was in the exciting area of “things I thought I knew but didn’t.” To understand more, you have to start at the beginning — the very beginning.
I know that the Gospels are not in total agreement about the date of the Last Supper. The Synoptics (Matthew, Mark and Luke) see the Last Supper taking place on the first day of Passover, which began at sundown on Thursday. John, on the other hand, sees the Last Supper taking place on the evening before Passover, which according to John would have begun Friday at sunset. I was aware of a group of Christians in the early church called the “Quattuordecimans” (”Fourteeners”) who celebrated Easter on the 14th of Nisan, the same day Jews celebrated Passover. For the Quattuordecimans, Easter could fall on any day of the week. Most Christians, however, celebrated Easter on the Sunday after Passover. There were some controversies between the two groups. The Council of Nicea (325), however, settled the matter and decreed that Easter would be on the first Sunday after the first full moon of the spring equinox in the northern hemisphere. The date of the equinox, with some slight astronomical inaccuracy, was determined as 21 March.
It would seem, then, that the question was solved in 325. What was the problem? The problem was not based on a deep, theological or mystical difference. The problem was based on an astronomical calculation: the length of the calendar year. The Julian calendar in use during the first 15 centuries of Christianity assumed that the solar year was 365 days and 6 hours. The problem is that the solar year is about 10 minutes and 48 seconds shorter than that. So what? Well, it really doesn’t make that much a difference — over a short period of time. However, over a longer period of time, it can make a big difference. By the time of Pope Gregory XIII (1582), after whom the Gregorian calendar is named, the difference meant that the spring equinox was falling on 11 March — some 10 days earlier!
Pope Gregory proposed — actually decreed — a new calculation to the calendar, which went into effect on 24 February 1582. In addition to using a more accurate measure for the length of the solar year, the Gregorian calendar “dropped” 10 days when it was inaugurated. It took several centuries before all countries accepted the new Gregorian calendar. Both political and denominational reasons made many hesitant to accept a “popish” change in the calendar. However, the Gregorian calendar slowly won out. When the British Empire and its colonies accepted it in 1752, 11 days had to be “dropped” to bring the calendar in line with the new calculations. The last of the Orthodox Christian countries to accept the Gregorian calendar was Greece in 1923. By that time, 13 days needed to be “dropped.” Thus by the mid 20th century, the Gregorian calendar was the dominant calendar in the world, although other — mostly religious — calendars, e.g. Muslim, Jewish, Persian, etc., still continue to exist.
The “problem” with the date of Easter has to do with when the spring equinox occurs. In the Gregorian calendar, it always occurs on 20 or 21 March. The present difference between the Gregorian and Julian calendars is 13 days (thus the spring equinox in the Julian calendar is on about 8 March). In 2100 the difference will be 14 days. To help bridge the gap, in 1923 some Orthodox churches proposed a revised Julian calendar, which was corrected against the solar year by dropping 13 days. However, not all of the Orthodox churches chose to adopt the revised Julian calendar and those that did chose it to calculate the dates of fixed feasts and not the date of Easter. In 1997 at a meeting in Aleppo, Syria, the World Council of Churches proposed that the date for Easter be calculated using astronomical observations for the spring equinox and full moon based at the meridian of Jerusalem. This would have disregarded the question of Gregorian vs. Julian calendar and would have eliminated the disparity in dates. None of the member bodies of the World Council, however, adopted this solution.
For many Christians, especially in the west, the date for Easter is not all that important. For other Christians it is a point of identity. Ultimately the most import issue is whether the common observance of Easter by all Christians would give significant witness to the world. If it would not, then the date or dates of Easter are immaterial. If it would give greater witness, however, the question becomes what theological justification would there be for lessening the impact of Christian witness for what is basically an 11-minute-and-48-second difference in the length of our year?