DateTime::Calendar::Hebrew is the implementation of the Hebrew calendar. Read on for more details on the Hebrew calendar. The Hebrew/Jewish calendar is a Luni-Solar calendar. Torah Law mandates that months are Lunar. The first day of a month coincides with the new moon in Jerusalem. (In ancient times, this was determined by witnesses. Read the books in the bibliography for more info). The Torah also mandates that certain holidays must occur in certain seasons. Seasons are solar, so a calendar that can work with lunar & solar events is needed. WWW: http://datetime.perl.org/