Easter Sunday and Its Dating Methods - Facts

The annual celebration of Christ’s resurrection is dated by the Easter Sunday. 

To maintain for each Easter Sunday, the same season of the year and the same relationship of the astronomical full moon that preceded the occurrence of Christ’s resurrection in 30 A.D., the Easter dating method was introduced. 

The Easter Dating Method achieved in 1583 A.D. by Pope Gregory the 13th, and his astronomers and mathematicians, using skill and common sense. 

They introduced a new revised Paschal Full Moon (PFM) Gregorian date’s table. This table replaced the original 326 A.D “19 PFM dates” table in the Julian calendar. 

Before the introduction of the PFM Gregorian dates, Easter Sunday was celebrated as thus; 

31 A.D to 325: Easter Sunday was celebrated either; 

1. On or just after the first day of the Jewish Passover (without considering which of the week that Easter day occurred). 
2. On a Sunday close to or on the first Passover day. 

Both of the listed methods existed continuously throughout this period. 

326 A.D. to 1582 A.D.: Easter Sunday is always celebrated on one of the 35 dates March 22 to April 25. The Easter Sunday on the Julian calendar is in use at that time.  Also the Easter Sunday Date for any given year is not determined by March Equinox date for that year. The Easter Sunday during this period became defined as the Sunday succeeding the PFM date for the year by using a simple “19 PFM dates” table. 

1582: The Gregorian calendar 

The Julian calendar was replaced by the Gregorian calendar in October 1582 to re-align March 20 (and therefore Easter) with the seasons by removing 10 dates October 5 to 14, 1582.   This replacement did not occur until later in many countries e.g. in September 1752 in England 

The Gregorian calendar very closely maintains the alignment of seasons and calendar dates by having leap years in only 1 of every 4 century years, namely, those divisible exactly by 400.   One additional February 29 date will need to be removed in about 4140 A.D., therefore Easter calculations will need to use the changed Days of Week of PFM dates when the exact year for this removal is decided. 

March 20 (not March 21) is the most common Gregorian Equinox date from 1583 to 4099 A.D. 

Historically, references to March 21 have caused mistakes in calculating Easter Sunday dates.   March 20 has become the important date in recent Easter dating methods.   Despite frequent references to March 21, this date has no special significance to any recent Easter dating methods.  

Credits 

• Christian Prayer Books 
• Ronald W. Mallen (1995), Adelaide, South Australia.