in stages. The Alexandrian computus may have been adopted in parts of the south of Ireland in the first half of the 7th century. Among the northern English, the use of the Alexandrian computus over the Britanno-Irish cycle was decided at the Synod of Whitby in 664. The Alexandrian computus was finally adopted by the Irish colonies in northern Britain in the early 8th century. Modern calls for a reform of the date of Easter After the Gregorian reform of the calendar by promulgation in 1582, the Roman Catholic Church continued to follow the same method for computing the date of Easter but the resulting date differed from that computed using the Julian Calendar due to the difference in time regarding when the vernal equinox was deemed to occur and when the relevant full moon fell. The Protestant churches of the Christian West all eventually adopted the Gregorian Calendar at various later stages. The Eastern Orthodox Church and the majority of the Christian East continue the older practice aligned to the Julian calendar. Several attempts have sought to achieve a common method for computing the date of Easter. In 1997 the World Council of Churches proposed a reform of the method of determining the date of Easter at a summit in Aleppo, Syria: Easter would be defined as the first Sunday following the first astronomical full moon following the astronomical vernal equinox, as determined from the meridian of Jerusalem. The reform would have been implemented starting in 2001, since in that year the Eastern and Western dates of Easter would coincide. But this reform was never implemented. See also Computus Epact Sardica paschal table Gregorian calendar Reform of the date of Easter Notes References Jones, Charles W. Bedae Opera de Temporibus. Cambridge: Mediaeval Academy of America, 1943. pp. 3–104. McCarthy, Daniel and Ó Cróinín, Dáibhí. "The 'Lost' Irish 84-year Easter Table Rediscovered", Peritia, 6–7 (1987–88): pp. 227–242. Mosshammer, Alden A. The Easter Computus and the Origins of the Christian Era. Oxford: Oxford University Press, 2008. . Walsh, Maura and Ó Cróinín, Dáibhí. Cummian's Letter De controversia paschali and the De ratione conputandi. Toronto: Pontifical Institute of Medieval Studies, 1988. Wallis, Faith. Bede: The Reckoning of Time. Liverpool: Liverpool University Press, 2004. pp. xxxiv–lxiii. External links Catholic Encyclopedia: "Easter Controversy" Philip Schaff's History of the Christian Church, volume 3, section 79: "The Time of the Easter Festival" Petition for the unification