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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 consists of a short description
of the content of this new book, which is available via this website,
and a concise curriculum vitae of its author. |
This book explains, by following the mainstream
of the history of computus (i.e. Paschal reckoning
developed from early third century for determining Julian or Alexandrian
calendar dates of Paschal Sunday) which shortly after AD 250 rose in Alexandria
(Egypt) to ultimately in AD 1582 (turning point in the history of chronology)
flow into an astronomically more realistic method for determining Gregorian
calendar dates of Easter, how at the time in Alexandria calendar dates of
Paschal Sunday depended on phases of the moon and how recently the three lost
fundamental Metonic lunar cycles constructed in Alexandria before the first
council of Nicaea in AD 325 (turning point in the history of Christianity)
were reconstructed by the author of this book on the basis of the Six
Millennium Catalog of Phases of the Moon compiled by
NASA’s eclipse expert Fred Espenak.
Its author, Jan Zuidhoek, was born in 1938, studied mathematics,
physics, and astronomy at the university of Utrecht from 1960 to 1969, and was a teacher of mathematics from 1970 to 2001 at
Gymnasium Celeanum in Zwolle. After having gone
deeply into the history of chronology and of early Christianity, which resulted in his webpages “Christian Era and Universal Time”
and “Dionysius Exiguus’
Paschal Table”, he became fascinated by the
Alexandrian computus. In 2009 he succeeded, using the
Six Millennium Catalog, in reconstructing the lost predecessor of the
lost Metonic lunar cycle underlying the famous 19‑year Paschal cycle of the great third
century Alexandrian computist Anatolius which had survived
as a part of the third or fourth century Latin text De ratione paschali. The presentations he
gave at international conferences on the science of computus
at the university of Galway in 2010 and 2018 resulted, respectively, in 2017 in
a pioneering article, entitled “The initial year of De ratione paschali and the relevance of its paschal dates”, and
in 2019 in his first book, entitled “Reconstructing Metonic 19-year
Lunar Cycles” and reducing the article to a preparatory study. It is from the
revised edition (2021) of his first book that this new book (2023) was
developed.
© Jan Zuidhoek 2023‑2026
(updated 12-10-2026)