This year, as with most years in the past, we have two Easters. The western church, those known as Catholic and Protestant, celebrated last Sunday, April 13. We of the Eastern Orthodox world will celebrate this coming Sunday, April 19. While you of the west are enjoying your lamb and ham and chocolate bunnies, we are still making do with a Lenten diet of greens and beans. But Pascha is coming (virus or no virus) and we will rejoice and celebrate, even if only virtually.
Why is it that we have this difference? I will tell you one thing certain, it not because of the calendars. The starting point has to be that though there are two celebrations and two (three if you consider the Jewish lunar calendar as well) calendars, we all celebrate the same day in the west and the same, though often different day in the east.
Keep in mind two basic facts while we try to untangle this weed patch. First, we are all in agreement as to what to call each day. The days of the week are not in dispute and it has been so since the time of Moses. You can be dead certain that 14,000 days ago (which is 2,000 weeks or about 38 years) was the same day as when you read this. The second concerns the cornerstone of our time and date keeping. We can calculate the day and time of the Vernal Equinox to a fare-the-well. This is so because that celestial event occurs without reference to anything human. It is outside our capability to modify our world. But is is readily calculated.
Why the Vernal Equinox? Firstly, because the execution of Jesus of Nazareth took place at the end of Passover. The date of Passover is determined first from the Jewish calendar which is in turn a lunar calendar with its own peculiarities. It has served the Jews for millennia and the date of Passover is always 15 Nisan. The Wikipedia entry for “Jewish Calendar” makes for interesting reading. Of primary interest is the fact that months can be either 29 or 30 days in length to compensate for the fact that one lunar revolution is about 28.5 days.
Of course, the crucifixion is not a concern to Jews, but it has long been held in the Orthodox Church that the observance of that event and of His resurrection, Pascha, should always follow Passover. After the Great Schism in 1054 AD, the western Church went its separate way. At some point, the west modified the means of determining the appropriate date and the difference has existed ever since. Try the Wikipedia entry for Computus for a brief explanation. While not fully correct, the rubric is that the west determines the date as the first Sunday after the first full moon and after the Vernal Equinox. The Orthodox version adds “after Passover” to the formula.
Note that in all this, the solar calendars still in use, the Gregorian and Julian, have no bearing on this determination. And here is where an interesting difference occurs within the Orthodox Church. In the Roman world, the calendar was somewhat arbitrarily decided and could often be a political plaything. There was a method but by the time of the reign of Julius Caesar, it was a mess and he determined to reform it. Enlisting the aid of Greek mathematicians and astronomers, a formula was developed that took the adjustments made to compensate for the sun’s rotation time (approximately 365.25 days) and it took effect by edict on January 1 of the 709th year since the founding of Rome, the year we now know as 45 BC.
That calendar held until 1582, by which time it had slipped* about 10 days. Pope Gregory XIII decided that a correction must be made but rather than simply adjusting the date, he had further adjustments made to the calendar scheme to reduce the rate of slippage. Thus, October 4, 1582 was followed by October 15th and in 1584 for the first time , many children were born on a day that would not occur again for four years. They should consider themselves lucky. Under the old, pre-Julian calendar, there were frequent periods when the date could not be known.
How the two calendars come to bear requires another dip into history. The short story is this. Once the Gregorian calendar was adopted by Catholic countries, then most western countries followed suit. This lead to a real division in the Orthodox Churches, as many Orthodox churchmen refused to adopt anything related to the Catholic Church, and surely, the Gregorian calendar was foremost among them. The last European country to adopt the Gregorian calendar was Greece and then only in 1923.
As things now stand, many Orthodox jurisdictions, the Serbian and Russian most prominent among them, still use the Julian calendar which now is 13 days different from the Gregorian. Thus, we of the Greek Orthodox Church celebrate Pascha on April 19. Our Serbian friends down the street will celebrate on that same day but their date will be April 6. It is important to note that we celebrate on the same day, regardless of how we name that date. This is why our western friends mostly observe a different day, because they use a different method to set the day.
One more thing to add to the confusion: While the Serbian Church will mark Pascha on the same day as we do, their calendar will have them celebrate Christmas in January. It will still be December 25, Julian calendar, even though we call that day January 3.
calendar slippage. Neither the earth’s rotation around the sun or that of the moon around earth, are exact multiples of the earth’s spin period. All calendars try to take this into account and schemes such as leap years are a means of compensating. Ultimately the date for events such as the Vernal Equinox will change, as from March 21 to 22 or 20, for example.