**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.**

**© Jan Zuidhoek 2019‑2022**