[rhrpkdug] Factor the calendar

Period	Days	Factorization
Year	365	5 * 73
Leap Year	366	2 * 3 * 61
Julian Olympiad	1461	3 * 487
Gregorian Cycle (400 years)	146097	3 * 3 * 3 * 7 * 773

Synodic month approximations

	Mean month (days)	Days in cycle	Factorization
Chinese Taichu Calendar (old)	29 43/81	2392	2 * 2 * 2 * 13 * 23
Orthodox Easter computus	29 499/940	27759	3 * 19 * 487
Newton	29 26/49	1447	1447
Hebrew calendar molad	29 13753/25920	765433	131 * 5843
Hindu Surya calendar (modern)	29 7087771/13358334	394479457	394479457
Yerm Lunar calendar	29 451/850	25101	3 * 3 * 2789
Gregorian Easter computus	29 37405943/70499183	2081882250	2 * 3 * 3 * 3 * 3 * 5 * 5 * 5 * 7 * 19 * 773
Tibetan Phugpa calendar	29 3001/5656	167025	3 * 5 * 5 * 17 * 131
Dee Easter computus	29 864071/1628531	48091470	2 * 3 * 5 * 7 * 17 * 19 * 709
Hindu Arya calendar (old)	29 2362563/4452778	131493125	5 * 5 * 5 * 5 * 61 * 3449
Tabular Islamic calendar	29 191/360	10631	10631

Many values from Length of the Lunar Cycle.

The "Days in cycle" is the number of days for there to be an integer number of months. Multiply the mean month by the denominator.

The successor to the Taichu calendar used a non-constant model (cubic). The successor to that, the modern Chinese calendar, uses astronomical observations.

Noting that the Gregorian cycle (400 years) and the Hebrew calendar molad share no common factors, the Gregorian computus could be, and arguably should be, worse. Multiply the two periods to get a cycle of 111827465001 days.

The Metonic Cycle = 235 months = 5 * 47.