Easter schedule dating system
At that time the Roman world used the Julian Calendar (put in place by Julius Caesar).The Council decided to keep Easter on the same Sunday throughout the Christian world.The Eastern Christian churches still determine the Easter dates using the older Julian Calendar method.The statement that Easter Day is the first Sunday after the full moon that occurs next after the vernal equinox, is only an approximate statement of the actual ecclesiastical rules.So in some places in the world Easter was on the same Sunday as the astronomical Full Moon.For dates of Easter and other Christian observances, see the Selected Christian Observances service.Thus, the civil date of Easter depends upon which tables - Gregorian or pre-Gregorian - are used.
Easter is an annual festival observed throughout the Christian world.Inevitably, the date of Easter occasionally differs from a date that depends on the astronomical full moon and astronomical vernal equinox.In some cases the difference may apply to some parts of the world and not to others because two different dates separated by midnight are always simultaneously in progress on the Earth.Universal adoption of this Gregorian calendar occurred slowly.
By the 1700's, though, most of western Europe had adopted the Gregorian Calendar.
For example, in 1962 the astronomical full moon occurred on March 21, UT=7h 55m - about six hours after astronomical equinox.