Why The Moon Determines When We Celebrate Easter


An astronomer at New York's Hayden Panetarium reminds us that when we celebrate Easter has little to do with the days of the month but much to do with the heavens.

The first full moon of spring, which is expected to arrive later today, is officially designated as the Paschal Full Moon. Traditionally, Easter is observed on the Sunday after the Paschal Full Moon. If the Paschal Moon occurs on a Sunday, Easter is the following Sunday. In 1582, Pope Gregory XIII decreed that, using the Gregorian calendar to track the moon, Easter could fall as early as March 22 or as late as April 25.

Joe Rao, who serves as an instructor at the Hayden Planetarium and writes about astronomy for The New York Times, reports that since the beginning of the 20th century, a proposal to change Easter to a fixed holiday rather than a movable one was widely circulated, and in 1963, the Second Vatican Council agreed, if a consensus could be reached among Christian churches. The second Sunday in April has been suggested as the most likely date.