A leap cycle of 128 years contains 31 leap days and thus overall 46751 days or 1536 twelfth-of-a-year months, spanning a bit more than 1583 lunations. Its mean year length is 365.2421875 days or 365 days, 5 hours, 48 minutes and 45 seconds. It does not contain an integer number of 7-day weeks and its smallest superset to do so is the 896-year leap cycle. This leap cycle was proposed by Johann von Mädler around 1864 as a better alternative to the Julian 4-year and the Gregorian 400-year leap cycle.
Leap rule[]
For the 128-year cycle, usually a single Olympiad leap day is dropped. Otherwise, four leap days within each subcycle would have to be delayed by one year. Alternatively, the distance between leap days could be fixed to 1508 days, 215 or 216 weeks, 49 or 50 months, i.e. about 4.129 years, so the leap date floats through the year over the course of the subcycle.