**Jan Zuidhoek, the author of this new study,
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 steeped himself in the fields
of history of mathematics, history of early Christianity, and chronology, the
author became fascinated by the computus paschalis, i.e. the science developed
from the beginning of the third century on behalf of the determination of the
date of Paschal Sunday. In 2009 he succeeded in determining the initial year
(AD 271) of De ratione paschali, i.e.
the medieval Latin text containing the Paschal tract of the famous third century
Alexandrian computist Anatolius, founder of the modern way of determining the
date of Easter. He did it by reconstructing, on the basis of NASA’s Six
Millennium Catalog of Phases of the Moon, the proto-Alexandrian 19-year lunar
cycle defined to be the Metonic 19-year lunar cycle Anatolius must have used to
construct his legendary 19-year Paschal cycle. The reconstruction in question
was the subject of his contribution to the international conference on the
science of computus which took place at the university of Galway in 2010. It
was published in 2017 as an article in the proceedings of that conference under
the title “The initial year of De ratione
paschali and the relevance of its paschal dates”.**

**This new study developed from the
presentation the author gave at the university of Galway in June 2018 under the
title “Reconstructing the Alexandrian 19-year lunar cycles”. Because the paper
in question was accepted outside the theme of the conference, it should not be
included as an article in the proceedings of the conference. Therefore the
author, convinced of the relevance of his recent discoveries, decided, in view
of his old age and in order not to lose time, to publish these new results on
his own in the form of this book, however not without dedicating it to his
great teacher and friend Dr. Daniel P. Mc Carthy, who, always attentive, went
on critically following the development of his ideas during the last ten years,
and expressing his gratitude to his beloved wife Marie Luijters for her
unconditional patience with his new ambition.**