This webpage belongs to www.janzuidhoek.net, which is a website promoting [Jan Zuidhoek (2019) Reconstructing Metonic 19-year Lunar Cycles (on the basis of NASA’s Six Millennium Catalog of Phases of the Moon): Zwolle], and shows section Summary of this pioneering book, which is available via this website.
Summary
It is the development the Alexandrian Metonic 19-year lunar cycle
underwent that formed the mainstream of the history of the computus paschalis
which had risen in third century Alexandria (Egypt) and would in the year 1582
flow into the modern method which since then is used in order to determine the
Gregorian calendar date of Easter Sunday. Between the active construction of
the very first Metonic 19-year lunar cycle by the Alexandrian computist
Anatolius, somewhere between AD 250 and 270, and the replacement of the Julian
calendar with the Gregorian calendar (in the year 1582) it happened only one
time, namely somewhere between AD 300 and 324, in any case already before
the first council of Nicaea, that (under the auspices of the church of
Alexandria) a radically new Alexandrian Metonic 19-year lunar cycle was actively constructed. After having
reconstructed (on the basis of NASA’s Six Millennium Catalog) both of these
ante-Nicene Metonic 19-year lunar cycles, we establish that:
1) the first of them (referred to as ‘Anatolius’ 19-year
lunar cycle’) is nothing but the lost proto-Alexandrian 19-year lunar cycle
(reconstructed in 2009);
2) the second of them (referred to as ‘the archetypal
Alexandrian 19‑year lunar cycle’) is nothing but the lost ante-Nicene
archetype from which after AD 325 one after another each of the three well‑known
post-Nicene Alexandrian Metonic 19‑year lunar cycles was obtained simply
by moving only 1 of the 19 different dates of its immediate predecessor one day
forward or back (see Table 8);
3) the cause of the 2-day gap between them (referred to as
‘the ante-Nicene Alexandrian 2-day gap’) must be sought in the transition from
the more Jewish Christian world of the third century to the more Gentile Christian
world of the fourth, as a result of which Alexandrian computists began to use
the Egyptian lunar calendar more familiar to them instead of the Alexandrian
version of the Jewish lunar calendar;
4) both Anatolius’ 19-year lunar cycle and the sequence of
dates of Paschal Sunday generated by it according to the old Alexandrian
Paschal rule have de facto lower limit date 23 March;
5) the archetypal Alexandrian 19-year lunar cycle has de
facto lower limit date 21 March but the sequence of dates of Paschal
Sunday generated by it according to the new Alexandrian Paschal rule has de
facto lower limit date 22 March (the same applies to the well-known three
post-Nicene Alexandrian Metonic 19-year lunar cycles).
We conclude that Anatolius may be considered to be the
founder of the efficient Metonic 19-year lunar cycle method of determining the
Julian calendar date of Paschal Sunday from which thirteen centuries later the
Italian astronomer Luigi Lilio and subsequently the German mathematician
Christoph Clavius could develop a modern, astronomically more correct, system
for determining the Gregorian calendar date of Easter Sunday.
© Jan Zuidhoek 2019-2021