Ecclesiastical full moon
An ecclesiastical full moon is formally the 14th day of the ecclesiastical lunar month (an ecclesiastical moon) in an
Schematic lunar calendars can and do get out of step with the Moon. A useful way of checking their performance is to compare the variation of the astronomical new moon with a standard time of 6 a.m. on the last day of a 30-day month and 6 p.m. (end of day) on the last day of a 29-day month.
Beginning in the medieval period the age of the ecclesiastical moon was announced daily in the office of
In the
Paschal full moon
The paschal full moon is the ecclesiastical
The calculations to determine the date of the paschal full moon can be described as follows:
- Nineteen civil calendar years are divided into 235 lunar months of 30 and 29 days each.
- This period of 19 years (the metonic cycle) is used because it produces a set of civil calendar dates for the ecclesiastical moons that repeats every nineteen years while still providing a reasonable approximation to the astronomical facts.
- The first day of each of these lunar months is the ecclesiastical new moon. Exactly one ecclesiastical new moon in each year falls on a date between March 8 and April 5, both inclusive. This begins the paschal lunar month for that year, and thirteen days later (that is, between March 21 and April 18, both inclusive) is the paschal full moon.
- Easter is the Sunday following the paschal full moon.
In other words, Easter falls from one to seven days after the paschal full moon, so that if the paschal full moon is on Sunday, Easter is the following Sunday. Thus the earliest possible date of Easter is March 22, while the latest possible date is April 25.
Earliest Easter
In 1818, as a paschal full moon fell on Saturday March 21 (the ecclesiastical fixed date for the Equinox), Easter was the following day—Sunday March 22—the earliest date possible. It will not fall on this date again until 2285, a span of 467 years.[4]
Latest Easter
In 1943 a full moon fell on Saturday March 20. As this was before March 21, the next full moon, which fell on Sunday April 18, determined the date of Easter—the following Sunday, April 25. It will not fall on this date again until 2038, a span of 95 years.[5]
For a detailed discussion of the paschal computations, see Date of Easter (the Computus).
Easter tables
By the middle of the third century AD computists of some churches, among which were the
The computational principles developed at Alexandria eventually became normative, but their reception was a centuries-long process during which Alexandrian Easter tables competed with other tables incorporating different arithmetical parameters. So for a period of several centuries the sequences of dates of the paschal full moon applied by different churches could show great differences (see Easter controversy).
See also
- Computus
- Dionysius Exiguus' Easter table
- Golden numbers
- Reform of the date of Easter
References
- ^ At medieval Exeter Cathedral, it was the next day's date and age of the Moon that were announced. Et omnibus in locis suis sedentibus sit ibi quidam puer...paratus ad legendum leccionem de Martilogio, absque Iube domine, sed pronunciondo primo loco numerum Nonarum, Iduum, Kalendarum, et etatem lune qualis erit in crastino... (And when all are sitting in their places let a boy be there ready to read the Martyrology beginning with Iube domine, but first saying the number of Nones, Ides, Kalends, and what the age of the moon will be on the morrow...) J. N. Dalton, ed., Ordinale Exon. vol. 1, Henry Bradshaw Society, London, 1909, p. 37.
- ^ The Book of Common Prayer according to the use of The Episcopal Church, Seabury Press, New York, pp. 21-22.
- ^ Montes, Marcos J. "Calculation of the Ecclesiastical Calendar". Archived from the original on November 3, 2008. Retrieved 2008-01-12.
- ^ "Easter Dating Method - Calculate the Date of Easter Sunday". www.assa.org.au. Retrieved 2022-09-29.
- ^ Bureau, US Census. "Easter Dates from 1600 to 2099". Census.gov. Retrieved 2022-09-29.
- ^ Georges Declercq, Anno Domini: The origins of the Christian era (Brepols, Turnhout, Belgium, 2000)