If the Fast-breaking (Fiṭr) of the Christians were identical with their Passover, or if it fell always at one and the same invariable distance from Passover, both would revolve through the years either on the same days, or parallel with each other on corresponding days. Since, however, Fast-breaking can never precede Passover, its earliest possible date falls by one day later than the earliest possible date of Passover, i.e. on the 22nd Adhâr (the 21st Adhâr being the earliest date of Passover). And the latest date of Fast-breaking falls by one week later than the latest date of Passover; because if one and the same day should happen (to be Fast-breaking and Passover, i.e. a Sunday), Fast-breaking would fall on the next following Sunday. In this case it would fall by one week later than Passover. If, therefore, Passover falls on its latest possible date (18th Nîsân), Fast-breaking also falls on its latest possible date, i.e. on the 25th Nîsân.
Therefore the days within which Fast-breaking varies are 35. And for the same reason the beginning of fasting varies parallel with Fast-breaking on the corresponding days, the earliest being the 2nd Shubâṭ, the latest the 8th Adhâr. Accordingly the greatest interval between the beginning of Lent and Passover is 49 days, the smallest interval 42 days.
Between the full moon of Passover and the new moon of Adhâr in a common year, of Adhâr Secundus in a leap-year, is an interval of
44 days, 7 hours, 6 minutes.
This new moon falls always between the beginning of the smallest interval and the greatest interval (between the beginning of Lent and Passover), and falls near the beginning of Lent. And this new moon has been made the basis of the whole calculation in this way: You observe the new moon of Shûbâṭ and consider which Monday is the nearest to it, the preceding one or the following. If this Monday lies within the Terminus Jejunii, i.e. between the 2nd Shubâṭ and the 8th Adhâr, it is the beginning of Lent. If, however, this Monday does not reach the Terminus Jejunii, and lies in the time before it, that new moon is disregarded, and you repeat the same consideration with the following new moon. In this way you find the beginning of Lent.
As we have mentioned already, Passover may proceed towards the beginning of the year as far as the 21st Adhâr, which is its earliest possible date. If full moon falls on this day and it is a Sabbath, the year is a common year, the new moon by which you calculate falls on the 4th Shubâṭ and the preceding Monday, which is the nearest Monday to this date, and therefore the beginning of the Terminus Jejunii is the 1st Shubâṭ, if the year be a leap-year, but the 2nd Shubâṭ if the year is a common year. This date lies within the Terminus Jejunii, and so it is the beginning of Lent.
