Have you ever wondered why Easter in the Orthodox and Western churches often fall on different dates? This year, Western churches celebrated Easter on March 27, while for Orthodox churches Easter falls over a month later on May 1. The reasons for the difference are surprisingly complex, as explained in “A Tale of Two Easters.”
Both Western and Orthodox churches define Easter as “The first Sunday after the first full moon on or after the vernal equinox.” However, the two churches calculate it very differently.
Western and Orthodox churches follow different calendars. Western churches use the Gregorian Calendar, the modern calendar established in the 16th century by Pope Gregory XIII that most of the world uses today. Orthodox churches, however, follow the Julian calendar that Julius Caesar initiated in 46 B.C.
The two churches also interpret “full moon” and “vernal equinox” differently. The Western Church uses the fixed date for the vernal equinox (usually thought of as the first day of spring). It also bases Easter on the “ecclesiastical moon,” which is calculated by tables that the church creates and doesn’t necessarily match up with the real astronomical full moon. The Orthodox Church uses the actual astronomical full moon and equinox, as observed along the meridian of Jerusalem.
In 1997 the Council of World Churches proposed simply using the most astronomically correct calculations, with Jerusalem as the point of measure. There have also been proposals to switch Easter to a fixed holiday, possibly the second Sunday in April, but no progress has been made with either of these proposals.