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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 presents a concise curriculum
vitae of the author of this new book, which is available via this website. |
Concise Curriculum Vitae of the
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. His post-retirement exploration of the history of
early Alexandrian computus were to no small extent fueled by the invitations he received to participate in conferences at the university of Galway
on the science of computus in 2010 and in 2018, and resulted ultimately in 2023 in this new book.
Jan
Zuidhoek (in about 1995)
After having retired from education and
gone deeply into the history of mathematics, of chronology, and of early
Christianity, which resulted in his webpages Dionysius Exiguus’ Paschal Table
and Christian Era and Universal Time, he became fascinated by the history
of Alexandrian computus, i.e. the Alexandrian way of
practicing the computus paschalis,
which is the science developed from the early third century (mainly in Rome and
in Alexandria) to determine Julian or Alexandrian calendar dates of Paschal
Sunday by constructing lunar cycles of the Paschal full moon.
In 2009 he succeeded, by using Espenak’s Six Millennium Catalog of Phases of the Moon, in reconstructing the
lost Metonically structured (19‑year) lunar cycle he referred to as the
‘proto‑Alexandrian lunar
cycle’ (0) from which the great third century Alexandrian computist
Anatolius originally (in about AD 260) started to determine his Paschal
dates, and in demonstrating the connection between the proto-Alexandrian lunar cycle and the Julian
calendar Anatolian lunar cycle underlying Anatolius’ famous 19‑year Paschal cycle which had survived as a
part of Anatolius’ Paschal table of 19 years being the core of the fourth
century Latin text De ratione paschali. These results were the
main subjects of the presentation he gave at the international conference on
the science of computus which took place at the
university of Galway in 2010. This presentation resulted in a pioneering
article entitled “The initial year of De
ratione paschali and the relevance of its paschal
dates”, which was published in 2017 in the proceedings of that conference.
At the aforesaid conference at the
university of Galway in 2018, the author presented a preview of
what he would publish later in book form:
1) his reconstruction (on the basis
of the Six Millennium Catalog) of the lost
Metonic lunar cycle generally referred to as ‘Anatolius’ lunar cycle’ (1) from
which Anatolius ultimately (in about AD 270) started in order to construct
his famous 19‑year
Paschal cycle;
2) his reconstruction (also on the
basis of the Six Millennium Catalog) of the
lost early fourth century Metonic lunar cycle he referred to as the ‘archetypal
Alexandrian lunar cycle’ (2) from which the three well‑known post‑Nicene Alexandrian Metonic lunar cycles would evolve;
3) his reconstruction (not on the
basis of the Six Millennium Catalog) of the
‘Festal Index lunar cycle’ (3) being the one of the three (well‑known) post‑Nicene Alexandrian Metonic lunar cycles which was compiled by the
unknown very first publisher of the famous Festal letters of bishop Athanasius
of Alexandria shortly after the bishop’s death in AD 373;
4) his explanation of the (ante-Nicene)
2‑day gap
between (1) and (2), i.e. the systematic difference of on average just over
2 days between corresponding calendar dates of (1) and (2).
Galway 2018
(with Immo Warntjes and Daniel P.
Mc Carthy)
The second of the two aforesaid
presentations was entitled “Reconstructing the Alexandrian 19-year lunar cycles”. Since the paper in
question was accepted outside the theme of the conference, it could not be
included as an article in the proceedings of the conference. It is therefore
that the author, convinced of the relevance of his discoveries in the field of
the history of computus, decided, in view of his old
age and to not lose time, to publish them in form of a book. In both his first
book (ISBN 9789090324678), published in 2019, and his new
book (ISBN 9789090370446), published in 2023, his reconstruction of
Anatolius’ lunar cycle (1), of the archetypal Alexandrian lunar cycle (2), and
of the Festal Index lunar cycle (3) are the main subjects.
Jan
Zuidhoek (in 2021)
The
improvement process the revised edition (2021) of the author’s first book,
entitled “Reconstructing Metonic 19-year lunar cycles”, underwent resulted in
2023 in his new book (ISBN 9789090370446), entitled “Reconstructing
Alexandrian Lunar Cycles”. Compared to its predecessor this new book has a new
look as well as a more correct title (because the two 19-year
auxiliary lunar cycles Anatolius used in constructing his Paschal cycle had no
Metonic structure) and a more correct subtitle (because the author of the Six
Millennium Catalog is not so much NASA as NASA’s
eclipse expert Fred Espenak), but ultimately the most
important difference between them turns out to be in their slightly different
Anatolius’ lunar cycle, which comes down to that the proto-Alexandrian lunar cycle (0) and Anatolius’
lunar cycle (1) are different in 1 out of their 19 calendar dates. The
difference in question is one of the three direct consequences of the revision
which Daniel Mc Carthy, the Irish scholar who in AD 1996 had solved the
seventeen centuries old mystery of Anatolius’ Paschal table of 19 years being
part of De ratione paschali,
relatively recently (in 2021) made of the eighteenth (AD 269) line of
Anatolius’ Paschal table, the other two direct consequences concern the two non-Metonic
Anatolian lunar cycles. In order to show the most important consequences of
this revision, the epilogue of this new book has been supplemented with a new Table 17
to correct its important Table 3 and a new Table 20
to show all six Alexandrian Metonic lunar cycles.
© Jan Zuidhoek
2023‑2025
(updated 1-2‑2025)