A Late Easter

A Late Easter

Since the Counsel of Nicaea met in 325 A.D. to resolve a number of disputes in the early Christian Church, the "moveable feast" of Easter in the Western Christian tradition has been reckoned as the first Sunday after the first full moon after the vernal equinox. This computation is modified slightly by a couple of simplifying conventions: the vernal equinox is taken as fixed on March 21, while the date of the full moon for ecclesiastical purposes may vary slightly from the astronomical date.

In any case, the result is that Gregorian Easter can fall anywhere from March 22 to April 25. In years like 2011, when one full moon appears shortly before the equinox (March 19), and the next full moon appears on a Monday, Easter comes very late: in this case, only one day before the last possible date. The last time Easter fell on the earliest possible date, March 22, was 1818, a performance that will not be repeated until the year 2285. The last time it fell on the latest possible date, April 25, was 1943; it will not do so again until 2038.

Holidays fixed by solar and lunar cycles always link me in my imagination to ancestors who began watching the skies, noting the patterns, teaching them to their descendants, and working out simple rules that could predict such complex behavior. The fact that we should be able to perceive order around us is the central mystery of my life.