1,273. Calculating Subsequent Months

Hilchos Kiddush HaChodesh 6:6

If the molad for a month is known, adding “1, 12, 793” will give one the time of the molad for the following month. One will be able to calculate the day of the week and at the hour of the day when it will occur, as well as how many chalakim of that hour will have passed.

Hilchos Kiddush HaChodesh 6:7

Therefore, if the molad for Nisan were to occur on Sunday, five hours and 107 chalakim after sunrise – in other words, “1, 5, 107” – adding the remainder for a lunar month of “1, 12, 793” will yield the time of the molad for Iyar: Tuesday night, five hours and 900 chalakim after nightfall, which equals “3, 5 900.” One could follow this process and calculate the time of the molad forever.