The Jewish holidays are celebrated in Israel officially and nationally and vacation days are set in accordance with them.
Judaism has its own calendar, the Jewish calendar, which has 12 lunar months based on the cycle of the moon. The Hebrew month starts with the first appearance of the new moon, the 15th of the month is when the moon is full and the month ends when the moon disappears (prior to its reappearance).
The Jewish holidays, some of which are very ancient, are based on the seasons of the year and mark the agricultural cycle. A calendar based on the appearance of the new moon, however, is not compatible with the natural cycle of a 365-day year (the length of time required for the earth to complete its orbit of the sun). A system was therefore developed in order to synchronize the lunar months with the solar year. Since the very beginnings of Jewish tradition, the custom of a leap year was instituted. Every two or three years, based on precise calculations, a year will have 13 months instead of 12, thus maintaining the synchrony between the lunar month system (and the Jewish holidays) and the seasons of the year. The “leap” - or doubled - month is always Adar, the sixth month in the Jewish calendar (approximately March-early April).
Unlike the Gregorian calendar, in which the days are counted from midnight of one night until midnight the following night, the days on the Jewish calendar are counted from sunset of one day until sunset of the next day. The Sabbath (Shabbat), for example, begins on Friday evening, and is called Erev Shabbat; therefore businesses in Israel close early on Friday afternoon. Shabbat ends on Saturday evening, called Motsa’ei Shabbat. The Jewish holidays similarly begin and end in the evening.
Some of the holidays in Israel are religious holidays connected with Judaism, while others are national holidays, connected with the history of the state since its establishment. The religious holidays are usually celebrated in a family or community setting, with each of the many Jewish ethnic groups in Israel observing its own customs alongside the Jewish laws for each holiday. Religious Jews observe the holidays according to long-standing traditions, which usually include special prayers. Secular Jews also observe the holidays, but over the years each family or social community has developed different holiday customs, which usually include large family dinners.
The cycle of the Jewish holidays begins with Rosh Hashanah, the Jewish New Year, in the Hebrew month of Tishrei, which usually coincides with late September and early October. Rosh Hashanah is followed by Yom Kippur (the Day of Atonement) and Sukkot (the holiday of Booths). During each of these holidays there are holy days, on which government offices and businesses are closed. Israelis tend to call Tishrei “the holiday period,” and use their days off work to go on vacation. Quite often important matters are postponed until “after the holidays.” Visitors to Israel should take into account that certain businesses will be closed for many days during this period, and hotels and vacation spots will be full of Israelis on vacation.
The second holiday period on the Jewish calendar is in the spring, when the holidays of Purim, Pesach (Passover) and Independence Day are observed, in the Hebrew months of Adar, Nissan and Iyar, which correspond with March, April and May. During Pesach many businesses are closed and the many days off work enable Israelis to go away on vacations.
Finally, another vacation period that has nothing to do with the Jewish calendar is the school vacation period - July and August. During these months, and particularly in August, many businesses and offices are closed for a week or two and all or most of the workers go on their annual vacations with their families, in Israel or abroad.