julian calendar determines the date for easter each year.
julian calendar determines the date for easter each year.
what determines the date for easter each year?
julian calendar
german protestant states used an astronomical easter between 1700 and 1776, based on the "rudolphine tables" of johannes kepler, which were in turn based on astronomical positions of the sun and moon observed by tycho brahe at his uraniborg observatory on the island of ven, while sweden used it from 1739 to 1844. this astronomical easter was the sunday after the full moon instant that was after the vernal equinox instant using uraniborg time . however, it was delayed one week if that sunday was the jewish date nisan15, the first day of passover week, calculated according to modern jewish methods. this nisan15 rule affected two swedish years, 1778 and 1798, that instead of being one week before the gregorian easter were delayed one week so they were on the same sunday as the gregorian easter. germany's astronomical easter was one week before the gregorian easter in 1724 and 1744. sweden's astronomical easter was one week before the gregorian easter in 1744, but one week after it in 1805, 1811, 1818, 1825, and 1829. two modern astronomical easters were proposed but never used by any church. the first was proposed as part of the revised julian calendar at a synod in constantinople in 1923 and the second was proposed by a 1997 world council of churches consulation in aleppo in 1997. both used the same rule as the german and swedish versions but used modern astronomical calculations and jerusalem time without the nisan15 rule. the 1923 version would have placed the astronomical easter one month before the gregorian easter in 1924, 1943, and 1962, but one week after it in 1927, 1954, and 1967. the 1997 version would have placed the astronomical easter on the same sunday as the gregorian easter for 2000–2025 except for 2019, when it would have been one month earlier.
computus
the discovery of the epact for computing the date of easter has been attributed to patriarch demetrius i of alexandria, who held office from 189 to 232. in the year 214 he used the epact to produce an easter calendar, which has not survived, which used an eight-year luni-solar cycle. a subsequent application of the epact to an easter calendar, using a sixteen-year cycle, is found in the paschal table of hipoolytus, a 112-year list of easter dates beginning in the year 222 which is inscribed on the side of a statue found in rome. augustalis, whose dates have been disputed from the third to the fifth century, computed a "laterculus" (little tablet) of easter dates. as reconstructed, it uses epacts (here the age of the moon on 1 january) and an 84-year luni-solar cycle to compute the dates of easter using a base date of a.d. 213. if we accept augustalis's earlier dates, his "laterculus" extends from 213 to 312 and augustalis originated the use of epacts to compute the date of easter.
epact