Easter Controversy - Third Phase

Third Phase

The Roman missionaries coming to Britain in the time of St. Gregory the Great (590–604) found the British Christians, and the Irish missionaries who evangelized the English from the north, adhering to a system of Easter computation which differed from that used in the Mediterranean world. This British and Irish system, on the evidence of Bede, fixed Easter to the Sunday falling in the seven-day period from the 14th to the 20th of its lunar month, according to an 84-year cycle. The limits of Nissan 14 – Nissan 20 are corroborated by Columbanus. The method used by the Roman Church was Nissan 15 – Nissan 21. The 84-year cycle, the lunar limits, and an equinox of March 25 also receive support from MacCarthy's analysis of Padua, Biblioteca Antoniana, MS I.27. Any of these features alone could have led to occasional discrepancies from the date of Easter as computed by the Alexandrine method.

This 84-year cycle (called the latercus) gave way to the Alexandrine computus in stages. The Alexandrine 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 Alexandrine computus over the Brittano-Irish cycle was decided at the Synod of Whitby in AD 664. The Alexandrine computus was finally adopted by the Irish colonies in northern Britain in the early 8th century.