Astronomy for “The Light of The Cosmos”

Date & time of Easter Vigil – Christ Our Light

Much debate and conflict has been spawned by efforts to determine the date this feast should be celebrated annually.  The difficulty comes in translating an “immovable feast” from a lunar to the Christian solar calendar (Julian, and now Gregorian), on which it becomes a movable feast (one that moves to a certain day of the week, the way Thanksgiving moves to a Thursday, instead of one that is always celebrated on a particular date, immovably, like a birthday).  The Council of Nicaea in 325 placed Easter on the first Sunday following the first full moon after March 20 (which is the vernal equinox, when the sun is directly above the earth’s equator).  This date allowed pilgrims to have moonlight for traveling to the great Easter festivals of that day.  According to this method of reckoning, Easter could be as early as March 22 and as late as April 25. (331, Klein: The Catholic Source Book; #1170, Catechism of the Catholic Church)

The Easter Vigil takes place at night. It should not begin before nightfall and should end before daybreak. It is never permitted to anticipate the Mass of Easter before the Easter Vigil or celebrate more than one Easter Vigil service in the same church (111, Huels: The Pastoral Companion; 197-note 2, Ordo: Canadian Conference of Catholic Bishops).

The precise time of the nightfall can be obtained from any basic astronomy program which is capable of calculating “the time of sunset” and then one adds 30 minutes to allow for the residual evening sunlight to dissipate.  The image below shows the precise time of sunset for April 19, 2014.

Nightfall = Time of Sunset + Dissipation of Residual Evening Light

Nightfall = 7:59 p.m. + 30 minutes

Therefore Easter Vigil 2014 A.D. begins at 8:30 p.m.