We owe this complicated formula, with its attention to both the sun (the equinox) and the moon (full phase), to a political compromise among Nicea's gathered factions.The Eastern Christians injected the irregular phases of the moon into the calculations—thus causing the "wandering" effect—because they wanted their lunar calendar to keep its historical (though problematic) role in determining important dates.Many of those first believers expected Jesus to return soon, a hope that (some scholars believe) rendered such anniversaries unimportant for them.For these reasons, a single, universally accepted date for the event's celebration had little to no chance.This week, as they so often do, my Sunday School class of bright 12- and 13-year-olds posed a tough question: why did Easter fall on Evan's birthday last year, but it's falling on Abby's birthday this year?Though I couldn't answer on the spot, I knew I had a secret weapon back at the office—saved for just such an occasion: a short article by Farrell Brown, a retired chemistry professor with an interest in the historical interactions between science and religion.Ingeniously, it removed eight of the 250 leap days (February 29) occurring in each 1,000 years of the Julian calendar, thereby approximating more accurately the average number of days in a year—namely, 365.242.
Gregory's calendar inserted a correction to the Julian calendar from that time forward.
Here, as a public service for those still scratching their heads over the calendrical wandering of Easter, is Dr.
Brown's answer to my Sunday School kids' question—and thrown in for free, the story of why Easter dates still differ in different parts of the world: The date of Easter Sunday, a so-called movable feast day in the Christian Church year, may seem mysterious to many who celebrate it.
In fact, this was one of eight major topics considered by priests and bishops at the church's first Ecumenical Council in 325, in Nicea (present-day Turkey).
One unanimously accepted canon guaranteed that Easter would never fall on the beginning the Jewish Passover, perhaps reflecting Christian animosity towards the Jewish people for their perceived role in Jesus' death.