Standardization of Easter Celebration Date

The Catholic Church fixes the date of Easter, its celebration to mark the resurrection of Christ, using a method set out in AD 325 by the Council of Nicaea. In the first centuries AD, Easter was celebrated on different days by different groups of Christians, the Council of Nicaea sought to standardize it.

Role of Full Moon

Easter is now celebrated on the first Sunday after the full moon occurring on or after the spring equinox. Early Christians couldn’t simply wait to find out when the full moon would fall, then quickly celebrate Easter. They had to fit in Lent – 40 days of fasting – immediately beforehand, so had to know several weeks in advance when that full moon would fall, a task that could only be achieved by keeping astronomical records and projecting into the future.

Easter Dates 

• Table of Easter Dates (ranging from 1998-2038).
• Easter may occur on different dates in the Gregorian Calendar (used by Catholic and Protestant churches) and the Julian Calendar (used by the Orthodox church).

How the World Works: Astronomy: From Plotting the Stars to Pulsars and Black Holes
Anne Rooney

Background on Anne Rooney