How Often Does The Jewish Calendar Add A Month. Every month we add 29 days 12 hours and 793 halakim to the previous month’s molad, and announce the. Every month is either 29 or 30 days long, beginning (and ending) on a special day known as rosh chodesh (“the head of the month”).
In a leap year, there are 13 months. To find the corresponding jewish year for any year on the gregorian calendar, add 3760 to the gregorian number, if it is before rosh hashanah.