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the Jews keep the Passover, but follow the date determined by the church of
Rome and the church of Alexandria. Alexandria was presumably chosen
because of the renown in which the city was held for astronomical/astrological
knowledge, and the attempts already made there to produce tables giving the
date of Easter for successive years (notably by Anatolios [d. c.282], the
Alexandrian philosopher who become bishop of Laodicea, whose 19-year cycle
for calculating the date of Easter is still the basis of the calendrical systems in
use today); Rome because of its unquestioned prominence, at least in the West.
It was assumed that they arrived at the same date, though that cannot always
have been the case: the Alexandrian method used a 19-year cycle; the Roman
an 84-year cycle, so they were bound to diverge at some point. Indeed, later in
the century, Ambrose introduced the Alexandrian reckoning, because the
2
Roman reckoning was, in his view, faulty. Nevertheless, we can, I think, be
confident that the decision of the first Council of Nicaea was as I have stated
it: Easter, Pascha, the Christian Passover, is to be celebrated on the first Sunday
after the full moon after the vernal equinox (or, if full moon fell on a Sunday,
the following Sunday). 3
There are several points to be observed about this determination of the
date of Pascha. First of all, it has nothing to do with calendars as such;
whatever calendar you use, the date of the first Sunday after the full moon after
the vernal equinox is ascertainable, and nowadays, with our vastly improved
astronomical knowledge, the date could be readily determined (it would be
necessary to add where we are calculating this for, as the full moon takes place
at a particular moment, and could easily be on a different day in Tokyo and
London, say, but I think it would be easily agreed that the date should be
calculated for Jerusalem). Calendars come into the question of Pascha, because
of the need to determine in advance the date of Pascha, and these calculations
were originally (and still are) based on the calendar. Secondly, and I shall have
much more to say about this later, the date of Pascha involves a kind of

2 See his letter to the bishops of Aemilia and Romagna (ep. 23), determining the date of Easter for
the year AD 387, the year, incidentally, in which Augustine was baptized in Milan by Ambrose.
3 For bibliography on Easter and determining its date, see the articles in the Oxford Dictionary of the
Christian Church, ed. E.A. Livingstone (3rd edition, OUP, 1997, revised 2005), s.v. Easter, Paschal
Controversies, to which should be added: Paul F. Bradshaw and Maxwell E. Johnson, The Origins of
the Feasts, Fasts, and Seasons in Early Christianity (London: SPCK, 2011), 39–86; Faith Wallis’
introduction to Bede: The Reckoning of Time, trans. etc., by eadem, Translated Texts for Historians 29
(Liverpool University Press, 1999), xv–ci; Alden A. Mosshammer, The Easter Computus and the Origins
of the Christian Era (Oxford University Press, 2008). See also the still invaluable work by V. Grumel,
La chronologie (Paris: Presses Universitaires de France, 1958).

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