**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”. In the meantime (from 2001 to 2018) he kept an ultimately
sextilingual website on chronology.**

**This new study developed from the
presentation he 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.**