1,277. Calculating Any Molad in History

Hilchos Kiddush HaChodesh 6:14

Using the processes detailed throughout this chapter, it is possible to calculate the molad of any year or month, both those in the past and those in the future. Accordingly, one can take the number of years that have passed until Tishrei of a given year and divide them by 19. This will enable one to calculate the number of cycles and years of the current cycle that have passed. One adds the remainders of “2, 16, 595” for each cycle, “4, 8, 876” for each regular year of the current cycle that has not yet passed, and “5, 21, 589” for each leap year of the current cycle that has not yet passed. Totaling all this together, one then converts every 1,080 chalakim into hours, every 24 hours into days, and every seven days into weeks. Finally, one adds the remainder of the days, hours and chalakim to determine the molad of a given year.

Hilchos Kiddush HaChodesh 6:15

The molad of a year that is calculated using the method described above is actually the molad of Rosh Chodesh Tishrei. Adding “1, 12, 793” to the result will yield the molad of Marcheshvan; adding “1, 12, 793” to that will yield the molad of Kislev. Following this process, one can calculate the molad of the months forever.