This webpage belongs to, 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 fields of history of mathematics, of chronology, and of 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 initial year (AD 271) of De ratione paschali, i.e. the early medieval Latin text containing the legendary 19‑year Paschal cycle of Anatolius, the famous third century Alexandrian computist who had invented the underlying very first Metonic 19‑year lunar cycle, referred to as the proto‑Alexandrian cycle. His reconstruction of this 19‑year lunar 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 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 first council of Nicaea in AD 325 a completely different second Metonic 19‑year lunar cycle, referred to as the archetypal Alexandrian cycle, must have been constructed in Alexandria, he decided to write this very book, in which he describes not only his reconstruction of both the lost Alexandrian Metonic 19‑year lunar cycles in question, but also the development from the second of them to the so called classical Alexandrian cycle from which after the Gregorian reform in AD 1582, after preparatory work by the Italian astronomer Luigi Lilio, the German mathematician Christoph Clavius would develop a modern system for determining (Gregorian calendar) dates of Easter.



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