This webpage is part of www.janzuidhoek.com, which is a website promoting [Jan Zuidhoek (2021) Reconstructing Metonic 19-year Lunar Cycles (on the basis of NASA’s Six Millennium Catalog of Phases of the Moon): Zwolle], and shows a concise curriculum vitae of the author of this groundbreaking book, which is available via this website.

Concise Curriculum Vitae

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 the Gymnasium Celeanum in Zwolle. After having gone deeply into the history of mathematics, chronology, and early Christianity, ultimately resulting in his lucid webpage “Christian Era and Universal Time”, he became fascinated by the Alexandrian computus, i.e. the Alexandrian way of practising the computus paschalis being the science developed from the early third century for the purpose of determining (Alexandrian or Julian) calendar dates of Paschal Sunday.

In 2009 he succeeded, by using NASA’s Six Millennium Catalog of Phases of the Moon, in determining the original Metonic 19‑year lunar cycle underlying the fifth century Latin text De ratione paschali containing the legendary 19‑year Paschal cycle of the famous third century Alexandrian computist Anatolius. His reconstruction of this lost 19‑year lunar cycle, referred to as the proto‑Alexandrian cycle, was the subject 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 his 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. After having argued, at a similar conference in 2018, that shortly before the council of Nicaea in AD 325, turning point in the history of Christianity, in Alexandria a completely different Metonic 19‑year lunar cycle, referred to as the archetypal Alexandrian cycle, must have been constructed, he decided to write a book describing how he, again using NASA’s Six Millennium Catalog, reconstructed this very 19‑year lunar cycle as well as Anatolius’ 19‑year lunar cycle, the latter apparently being equal to the proto‑Alexandrian cycle. The first edition of this book, entitled “Reconstructing Metonic 19‑year Lunar Cycles (on the basis of NASA’s Six Millennium Catalog of Phases of the Moon)”, appeared in 2019; in this groundbreaking book he not only reconstructs both these historically important lost ante‑Nicene Alexandrian Metonic 19‑year lunar cycles and explains the (unmistakably ante‑Nicene) 2‑day gap between them but also describes the development from the archetypal Alexandrian cycle to the so called classical Alexandrian cycle from which around the great calendar reform in AD 1582, turning point in the history of chronology, a more realistic (but necessarily also more complicated) method for determining Gregorian calendar dates of Easter would be developed.

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