Fragment

The development the Alexandrian method for determining Julian or Alexandrian calendar dates of Paschal Sunday underwent is nothing less than the mainstream of the history of the computus (i.e. Paschal reckoning) which rose in third century Alexandria (Egypt) to ultimately (in sixteenth century Rome) flow into an astronomically more realistic method for determining Gregorian calendar dates of Easter. In this mainstream there were only two real rapids:
1) the solid construction (on the basis of temporarily lunar tables) of the proto Alexandrian lunar cycle (in about AD 260) and Anatolius’ lunar cycle (in about AD 270), the former being the (lost) Metonic lunar cycle from which the great third century Alexandrian computist Anatolius originally started to determine his Paschal dates, the latter the one from which he ultimately started in order to construct his famous 19 year Paschal cycle;
2) the solid construction of the archetypal Alexandrian lunar cycle, being the (lost) Metonically structured common archetype of the three well known post Nicene Alexandrian Metonic lunar cycles.
The proto Alexandrian lunar cycle and Anatolius’ lunar cycle were constructed in the third quarter of the third century, the archetypal Alexandrian lunar cycle was constructed half a century later, shortly before the first council of Nicaea in AD 325, turning point in the history of Christianity. And so it is not so much because of different moments of construction as because of different sets of computistical principles according to which they were constructed that the latter lunar cycle differs so much from the former ones. After having reconstructed them, we establish that:
1) there exists an ante Nicene 2 day gap between Anatolius’ lunar cycle and the archetypal Alexandrian lunar cycle, the cause of which must be sought exclusively in the transition in Alexandria and beyond 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 went to use the Egyptian lunar calendar much more familiar to them instead of the Alexandrian version of the Jewish lunar calendar);
2) both the proto Alexandrian and Anatolius’ lunar cycle have de facto limit dates 23 March and 20 April, both sequences of Paschal dates generated by them according to the old Alexandrian Paschal rule have de facto limit dates 23 March and 26 April;
3) the archetypal Alexandrian lunar cycle is the archetype from which after bishop Athanasius’ death in AD 373 one after another the three well known post Nicene Alexandrian Metonic lunar cycles would be obtained if not by simply adopting it then by simply adapting it by moving its saltus a few years afterward or forward;
4) the three well known post Nicene Alexandrian Metonic lunar cycles have, as well as the archetypal Alexandrian lunar cycle, de facto limit dates 21 March and 18 April, the three sequences of Paschal dates generated by them according to the new Alexandrian Paschal rule have de facto limit dates 22 March and 25 April.
We conclude that Anatolius can be regarded as the great founder, and the ante Nicene Alexandrian computists who constructed the archetypal Alexandrian lunar cycle and their great post Nicene follower Annianus as the most important developers, of the efficient Alexandrian Metonic lunar cycle method for determining Julian or Alexandrian calendar dates of Paschal Sunday from which, thirteen centuries after Anatolius’ death, because of the second great calendar reform in AD 1582, turning point in the history of chronology, an astronomically more realistic method for determining Gregorian calendar dates of Easter would be developed. ×