1,275. The 19-Year Cycle

Hilchos Kiddush HaChodesh 6:10

The calendar follows a 19-year cycle of seven leap years and 12 regular years. This cycle is called a machzor. This cycle was instituted because the number of days in 12 regular years and seven leap years including all their hours and chalakim, converting every 1,080 chalakim into hours and every 24 hours into days, equals 19 solar years of 365 days and six hours. The difference between the days of the lunar and solar calendars is only one hour and 485 chalakim, abbreviated as “1, 485.”

Hilchos Kiddush HaChodesh 6:11

In this 19-year cycle, the months are lunar and the years are solar. The seven leap years in each cycle are years 3, 6, 8, 11, 14, 17 and 19, appropriately abbreviated as “3, 6, 8, 11, 14, 17, 19.”