**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 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. The underlying reconstruction of this very 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 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, 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, turning point
in the history of chronology,
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 Sunday.**

**© Jan Zuidhoek 2019‑2021**