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This
webpage is part of www.alexandriancomputus.net, which supports the new book on
early Alexandrian Paschal reckoning [Jan Zuidhoek (2023) Reconstructing
Alexandrian Lunar Cycles (on the basis of Espenak’s Six Millennium Catalog of
Phases of the Moon): Zwolle]. This webpage shows section Summary of this new book, which is available via this website. |
The development the Alexandrian
method for determining Alexandrian or Julian calendar dates of Paschal Sunday
underwent is nothing less than the mainstream of the history of computus (i.e.
Paschal reckoning) which rose in third century Alexandria (Egypt) to ultimately
(in sixteenth century Rome) flow into an astronomically more realistic method
for determining Gregorian calendar dates of Easter. In this mainstream there
were only two real rapids:
1) the solid construction (on the
basis of at the time quite recent lunar tables) of the proto‑Alexandrian
lunar cycle (around AD 260) and Anatolius’ lunar cycle (around
AD 270), the former being the (lost) Metonic lunar cycle from which the
great third century Alexandrian computist Anatolius originally started to
determine his Paschal dates, the latter being the one from which he ultimately
started in order to construct his famous 19‑year Paschal cycle;
2) the solid construction (idem) of
the archetypal Alexandrian lunar cycle (around AD 320), being the (lost)
Metonically structured common archetype of the three (well-known) post‑Nicene Alexandrian Metonic lunar cycles.
The proto‑Alexandrian lunar cycle and Anatolius’
lunar cycle were constructed in the third quarter of the third century, the
archetypal Alexandrian lunar cycle was constructed already half a century
later, shortly before the first council of Nicaea in AD 325, turning point
in the history of Christianity. And so it must have been not so much because of
different moments of construction as because of different sets of computistical
principles according to which they were constructed that the latter lunar cycle
differs so much from both the former ones. After having
reconstructed them, we establish that:
1) there exists a 2‑day gap (in fact a systematic difference of
on average just over 2 days) between Anatolius’ lunar cycle and the archetypal
Alexandrian lunar cycle, the cause of which must be sought exclusively in the
transition in Alexandria and beyond from the more Jewish Christian world of the
third century to the more Gentile Christian world of the fourth (as a result of
which Alexandrian computists went to use the more familiar Egyptian lunar
calendar instead of the Alexandrian version of the Jewish lunar calendar);
2) both the proto‑Alexandrian
lunar cycle and Anatolius’ lunar cycle have de facto limit dates 23 March
and 20 April, both sequences of Paschal dates generated by them have,
according to the old Alexandrian Paschal rule, de facto limit dates
23 March and 26 April;
3) the archetypal Alexandrian lunar cycle is
the archetype from which after Athanasius’ death in AD 373 one by one each
of the three (well-known)
post‑Nicene Alexandrian Metonic lunar cycles was obtained either
by approving the archetype without any modification or by moving its saltus one
or two years forward or afterward;
4)
the three (well‑known) post‑Nicene Alexandrian Metonic lunar cycles have, as well as the archetypal
Alexandrian lunar cycle, de facto limit dates 21 March and 18 April,
the four sequences of Paschal dates generated by them have, according to the
new Alexandrian Paschal rule, de facto limit dates 22 March and
25 April.
We conclude that the Alexandrian
computists who constructed the three (lost) ante-Nicene
Alexandrian Metonic lunar cycles, in particular the great scholar Anatolius (he
died in about AD 282), can be regarded as the founders, their post-Nicene
followers Annianus (around AD 400), Dionysius Exiguus (around AD 500), and Beda
Venerabilis (around AD 700) as the great developers of the efficient
Alexandrian method for determining Julian calendar dates of Paschal Sunday from
and thanks to which in the end, thirteen centuries after Anatolius’ death, an
astronomically more realistic method for determining Gregorian calendar dates of
Easter could be developed.
© Jan Zuidhoek 2023‑2025