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Easter and Passover: Movable Dates

By CBSNews.com staff CBSNews.com staff

April 9, 1998 / 5:40 PM EDT / infoplease.com

The dates of Passover and Easter, as we all know, vary from year to year, but seem otherwise pretty straightforward -- that is, until you peer below the surface.

Calculating these dates involves a bewildering array of ecclesiastical moons and paschal full moons, the astronomical equinox and the fixed equinox -- not to mention three different calendar systems.

But before the movable feasts bring on vertigo, read below -- we've done our best to pin them down.

Passover, Gregorian Easter and Julian Easter

The Jewish liturgical year is the basis for Christian as well as Jewish movable feasts -- those annual holidays that do not fall on a fixed date but vary according to astronomical occurrences.

The celebration of Passover took place just before the Crucifixion and Resurrection of Christ, and the two holidays have been entwined from the beginning -- the word Pasch -- originally meaning Passover, came to mean Easter as well.

April 11 to 18: Passover
Passover, or Pesach in Hebrew, the holiday commemorating the Jews' exodus from slavery in Egypt, begins on the 15th day of Nisan, which is the seventh month in the Jewish Calendar, and ends on the 21st or 22nd of Nisan (in Israel it lasts seven days; outside Israel and among Reform Jews, it lasts eight).

Since Hebrew days begin and end at sundown, Passover begins at sundown on the day preceding the Nisan date (in other words, Passover begins this year at sundown on April 10). The Jewish Calendar, based on lunar and solar cycles, averages 354 days and begins around the time of the autumnal equinox, when the Jewish New Year, Rosh Hashanah, is celebrated.

April 12: Easter (Western churches)
Easter is calculated as the first Sunday after the paschal full moon that occurs on or after the vernal equinox. If the full moon falls on a Sunday, then Easter is the following Sunday. The holiday can occur anywhere between March 22 and April 25.

The Council of Nicaea in 325 established that Easter would be celebrated on Sundays; before that Easter was celebrated on different days in different places in the same year.

April 19: Easter (Eastern Orthodox Church)
The Orthodox church uses the same formula to calculate Easter, but bases the date on a slightly different calendar-the traditional Julian calendar insead of the more contemporary Gregorian one, the calendar that is most widely used today. As a consequence, both churches rarely celebrate Easter on the same day.

The theological inconsistency of two Easters has remained a thorny problem for the Christian Church. "It has long been recognized that to celebrate this fundamental aspect of the Christian faith on different dates," states the World Council of Churches, "gives a divided witness and compromises the churches' credibility and effectiveness in bringing the Gospel to the world."

Astronomical vs. ecclesiastical calculations

The formula for Easter -- "The first Sunday after the first full moon on or after the vernal equinox" -- is identical for both Julian and Gregorian Easters, but the definition of the vernal equinox and the full moon vary.

The Eastern Church sets the date of Easter according to the actual, astronomical full moon and the actual equinox as observed along the meridian of Jerusalem, site of the Crucifixion and Resurrection.

The Western church does not use the actual, or astronomically correct date for the vernal equinox, but a fixed date (March 21). And by full moon it does not mean the astronomical full moon but the "ecclesiastical moon," which is based on tables created by the church. These constructs allow the date of Easter to be calculated in advance rather than determined by actual astronomical observances, which are naturally less predictable.

This division between the Eastern and Western Churches has no theological basis, but neither is it an irrelevant technical skirmish. As the World Council of Churches has noted, much of Orthodox Christianity is located in the Middle East, where it has frequently been the minority religion, and in Eastern Europe, where until recently it faced hostility from communist governments.

The emphasis on honoring tradition and maintaining an intact religious identity was therefore crucial. Seen in this context, changing the rules governing its most important religious holiday chisels away at the foundations of an already beleaguered religious heritage.

East and West may coincide in 2001

A meeting organized by the Council of World Churches (in Aleppo, Syria, March 5-10, 1997) proposed a solution thought to be favorable to both East and West: both methods of calculating the equinox and the paschal full moon would be replaced with the most advanced astronomically accurate calculations available, using the meridian of Jerusalem as the point of measure. The proposed reform would begin in 2001 -- the year in which the Julian and Gregorian Easters next coincide.

Since the beginning of the century, a proposal to change Easter to a fixed holiday rather than a movable one has een widely circulated, and in 1963 the second Vatican Council agreed, provided a consensus could be reached among Christian churches.

The second Sunday in April has been suggested as the most likely date. Thus, this most movable of feasts may be moved in 2001 to a date that will satisfy both religious traditions and simplify a confusing calendrical morass.

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