Not quite "Why does Easter move?" - Canon Robin Ward

The Principal, Canon Robin Ward, reviews The Easter Computus and the Origins of the Christian Era by Alden A. Mosshammer (OUP £65) (978-0-19-954312-0) in today's Church Times.

The thesis of this book is simply stated. Conventional scholarship thinks that early in the sixth century a Scythian monk, Dionysius Exiguus, decided to replace the usual Dio­cletian calendar in the Easter table he was compiling, and use instead a system of his own devising, in which the consecutive numbering of the years began with the date of Christ’s birth. This caught on, and gave us the division of recorded time into BC and AD (now losing ground in academic circles to the dreary so-called Common Era).

But scholars also think that there is a howler in Dionysius’s mathe­matics, which is why virtually every­one agrees that AD 1 is not the date of Christ’s birth. Mosshammer doesn’t agree: he argues that Dionysius adopted an existing usage from the Church of Alexandria, in which a 19-year Paschal cycle and a method of calculating time accord­ing to a Christian era were inheri­ted from the work of Julius Africanus. Dionysius’s contribution was to pass this on to the West and thereby make it universal.

This thesis is argued with monu­mental erudition. In four parts, it explains why Easter moves according to a lunar cycle, how Easter tables were compiled and used, how dif­ferent ways of calculating the date of Easter developed in the patristic period, and how the calculation of time according to a Christian era related to the birth of Christ evolved. The reader must be warned to expect encounters with the epago­menal days with which the Egyptian month of Mesore ends, the 95-year exemplar of Cyril of Alexandria, the futile efforts of Anania of Shirak to supersede the Armenian mobile calendar, and the solar eclipse recorded by Phlegon in the fourth year of the 202nd Olympiad.

This is not the book to hand to a parishioner who asks you: “Why does Easter move?” or “When was Jesus born?” But if you have a taste for abstruse learning, classical, theological, and calendrical, the sort of taste which inspires the compilers of those useful annual ecclesiastical calendars that help us out so much, this is the Paschal book for you.

Photograph of the Easter Vigil at St Stephen's House, 2008