Reconstructing Alexandrian Lunar Cycles

This book explains, by following the mainstream of the history of computus (i.e. Paschal reckoning developed from early third century for determining Julian or Alexandrian calendar dates of Paschal Sunday) which shortly after AD 250 rose in Alexandria (Egypt) to ultimately in AD 1582 (turning point in the history of chronology) flow into a more realistic method for determining Gregorian calendar dates of Easter, how at the time calendar dates of Paschal Sunday depended on phases of the moon and how recently lost Metonic (19 year) lunar cycles constructed in Alexandria before the first council of Nicaea in AD 325 (turning point in the history of Christianity) were reconstructed on the basis of the Six Millennium Catalog of Phases of the Moon compiled by NASA’s eclipse expert Fred Espenak.

The author of this book 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 history of mathematics, chronology, and early Christianity, ultimately resulting in his lucid webpage “Christian Era and Universal Time”, he became fascinated by the Alexandrian computus. In 2009 he succeeded, by using the Six Millennium Catalog, in determining the Metonic lunar cycle underlying the legendary 19 year Paschal cycle of the great third century Alexandrian computist Anatolius which is part of the fourth century Latin text De ratione paschali. The two presentations he gave at international conferences on the science of computus at the university of Galway resulted in 2017 in a pioneering article and in 2019 in his first book, entitled “Reconstructing Metonic 19 year Lunar Cycles”, reducing that article to a preparatory study. It is from the revised edition of that book that this new book was developed.