Assertion: calendar's length | /r/HasProperty | 19 × 354
Facets:
Source sentences:
text: Each cycle of 30 years thus contains 19 normal years of 354 days and 11 leap years of 355, so the average length of a year is therefore ((19 × 354) + (11 × 355)) / 30 = 354.365… days, with a mean length of month of 1/12 this figure, or 29.53055… days, which closely approximates the mean synodic month (time from new Moon to next new Moon) of 29.530588 days, with the calendar only slipping one day with respect to the Moon every 2525 years.