Jewish holidays are determined each year by their placement on the Hebrew calendar and their corresponding placement on the Gregorian calendar. As an example, Chanukah always begins on the 25th of Kislev on the Hebrew calendar, but that date can be as early as November 26 or as late as January 6 on the Gregorian calendar.
The biggest Jewish holiday is the weekly observance of Shabbat or Sabbath. From Friday evening until past sundown on Saturday night, all “work” is considered a violation of the observance of Shabbat. Therefore, in the more observant communities driving a car, making a fire, taking pictures or even tying one’s shoes could be seen as doing work and are strictly forbidden. In Reform and Conservative communities, varying levels of observance from that practiced by the Orthodox are determined by the minhag (custom or tradition) of each synagogue or temple and by rabbinic bodies and authorities.
The Hebrew calendar is both a lunar calendar and a solar calendar. Because of their solemn nature, there are also a number of holidays that cannot fall on or be adjacent to Shabbat. Therefore, a sophisticated series of corrections - including the insertion of an extra month (Adar II) – over the course of a nineteen-year cycle has been implemented by rabbinic authorities. This also determines the weekly Torah readings read throughout the year in synagogues and temples.
Because the Hebrew calendar is based in part on the lunar cycle, ALL holidays begin at SUNDOWN on the evening before the listing. Therefore, if the holiday is observed on September 7, it begins at sundown on the evening of September 6.
On several Jewish holidays, the BSA has instituted a policy whereby it does not schedule activities or programs that would force Jewish Scouts to have to violate their religious observance by participating. The Gregorian dates for the holidays for the next four years are contained in a handy calendar that is available for download.