Date of Easter

The commonly stated rule, that Easter Day is the first Sunday after the full moon that occurs next after the vernal equinox, is somewhat misleading because it is not a precise statement of the actual ecclesiastical rules.

The actual conditions to determine the date for Easter are (1) Easter must be on a Sunday; (2) this Sunday must follow the 14th day of the paschal moon; (3) the paschal moon is that of which the 14th day (full moon) falls on or next follows the day of the vernal equinox; and (4) the equinox is fixed in the calendar as March 21. Easter can never occur before March 22 or later than April 25.

In order that the date for Easter be incontrovertibly fixed, and determinable indefinitely in advance, the Church constructed special tables for calculating the time of the paschal moon. There are three major differences to note between the ecclesiastical system and the astronomical system. (1) The 14th day of the paschal moon is not necessarily identical to the time of astronomical full moon. The ecclesiastical tables do not account for the full complexity of the lunar motion. (2) The vernal equinox has a precise astronomical definition determined by the actual motion of the Sun. It is the precise time at which the apparent longitude of the Sun is zero degrees. The actual date varies very slightly from year to year. In the ecclesiastical system the vernal equinox is fixed at March 21 regardless of the actual motion of the Sun. (3) The date of Easter is a specific calendar date. Easter starts when that date starts for your time zone. Astronomical phenomena occurs at a specific date and time all over the Earth at once.

Inevitably, the date of Easter occasionally differs from a date that uses an astronomical full moon and the astronomical vernal equinox. In some cases this difference may occur in some parts of the world and not in others because two dates separated by the International Date Line are always simultaneously in progress on the Earth.

1962 was such a case. In 1962, the astronomical full moon happened to occur about six hours after astronomical equinox. That full moon occured on March 21, UT=7h 55m. The ecclesiastical full moon, however, occured on March 20. The ecclesiastical equinox is fixed to be March 21; therefore, the ecclesiastical full moon occured before the ecclesiastical equinox. In the first case, the full moon followed the equinox; in other case, it preceeded the equinox. Following the rules, Easter, therefore, was not until the Sunday that followed the next ecclesiastical full moon. That occured on Wednesday, April 18 making Easter Sunday, April 22.

Similarly, in 1954 Easter was Sunday, April 18 because the first ecclesiastical full moon after March 21 fell on Saturday, April 17. However, the first astronomical full moon after the equinox happened to fall on April 18 at UT=5h. So in some places in the world Easter was on the same Sunday as the astronomical full moon.

The following are dates of Easter from 1980 to 2024:

1980  April 6	      1995  April 16	    2010  April 4

1981  April 19	      1996  April 7	    2011  April 24

1982  April 11	      1997  March 30	    2012  April 8

1983  April 3	      1998  April 12	    2013  March 31

1984  April 22	      1999  April 4	    2014  April 20

1985  April 7	      2000  April 23	    2015  April 5

1986  March 30	      2001  April 15	    2016  March 27

1987  April 19	      2002  March 31	    2017  April 16

1988  April 3	      2003  April 20	    2018  April 1

1989  March 26	      2004  April 11	    2019  April 21

1990  April 15	      2005  March 27	    2020  April 12

1991  March 31	      2006  April 16	    2021  April 4

1992  April 19	      2007  April 8	    2022  April 17

1993  April 11	      2008  March 23	    2023  April 9

1994  April 3	      2009  April 12	    2024  March 31

For other years, there is a date of Easter program in Data Services.

Ash Wednesday is 46 days before Easter. Lent - the season that begins on Ash Wednesday and ends at Easter - is said to be 40 days long because the six Sundays that occur in this period are not considered to be part of Lent.

The date of Easter is different in the eastern (Orthodox) Christian churches. The Julian calendar, which preceded the currently-used Gregorian calendar, is the traditional basis for the ecclesiastical calendar. (The Julian calendar was still used in much of eastern Europe until the early part of the 20th century.) In a congress held in 1923, the Orthodox churches adopted a modified Gregorian calendar and decided to set the date of Easter according to the astronomical full moon for the meridian of Jerusalem. However, these changes have not been universally implemented, and a variety of practices remain among the Orthodox churches