Jewish New Year Lunar Calendar. Am (latin anno mundi, the year of the world) and bce (before the common era) are the two dates of the jewish calendar. Jewish lunar calendar jews calculate the jewish new year using a lunar calendar. That is the signal for a new jewish month. The 12 lunar months of the hebrew calendar are the normal months from new moon to new moon: The current day on the calendar is determined by the time on the device from which you see the calendar. Rosh Is “Head” And Hashanah Is “The Year” (Head Of The Year)....