Jewish life is measured by the Hebrew calendar, which is based on a solar year comprising 12 lunar months. To correct the discrepancy between the lengths of the solar and lunar years, an extra month is added to the calendar every two to three years (according to a complex calculation that works out to seven of every 19 years being a leap year).
Although most Jews live in countries that use the Gregorian calendar, Israel included, the timing of Jewish festivals and holidays, from Rosh Hashanah and Yom Kippur to Tisha B’Av, is determined by the Hebrew calendar.
The Hebrew day lasts from sunset to sunset, which naturally means that holidays begin – and end – in the evening, when the sun sets. Also, each Jewish month begins with the appearance of the new moon. In ancient times, this depended on actually sighting the sliver of the new moon in Jerusalem.
Because people outside Israel couldn’t always know when exactly that happened, to be safe, they celebrated certain holidays for two days. This custom is still observed today by Jews living in the Diaspora.
Rosh Hashanah to Yom Kippur
The Hebrew calendar begins in early autumn on the first day of Tishri. Rosh Hashanah (the head of the year), the Hebrew New Year, is a two-day holiday (even in Israel) that also marks the beginning of the 10 days of repentance, a period of self-assessment that ends with Yom Kippur (the day of atonement), when tradition says God determines an individuals fate for the coming year.
Yom Kippur is the only holy day that has no agricultural or historical basis; it is purely ethical in its meaning.
Like on Shabbat, work is forbidden on these holidays. But whereas Rosh Hashanah is celebrated with festive meals for which cooking is permitted (not the case on the Sabbath), on Yom Kippur, we fast the entire 24-hour period, spend most of the days waking hours in prayer and introspection, and afflict ourselves in other ways, including no washing and no sexual intercourse.
Five days later, on Tishri 15, the seven-day (eight in the Diaspora) festival of Sukkot begins. Its first and last days (or, first two and last two days outside of Israel) have restrictions similar to those for Rosh Hashanah: Most work is prohibited but cooking is allowed, with certain limitations.
The festivals intermediate days, called hol hamoed, have many customs and rituals associated with them, but lack the restrictions of a holy day.
With its observance stipulated in the Torah, Sukkot has both an agricultural basis and a historical one. During Sukkot, we build temporary shelters (the word sukkot means booths or tabernacles), in which we are commanded to sleep and eat during the holidays duration. They are supposed to remind one of the dwellings used by the Israelites during their 40 years in the wilderness after the Exodus from Egypt. The holiday also celebrates the autumn harvest, and in antiquity it was a festival of pilgrimage to the Temple.
Shemini Atzeret and Simhat Torah
Shemini Atzeret and Simhat Torah fall immediately after Sukkot. In Israel, the two holidays are the same day; outside the country, they fall on consecutive days.
Shemini Atzeret (the eighth day of assembly) is of obscure meaning. Simhat Torah (rejoicing of the Torah) marks the festive end and the immediate restarting of the year-long cycle of reading the Five Books of Moses in synagogue.
After a break of two and a half months, Hanukkah (dedication) is celebrated beginning on Kislev 25 (around mid-December). A holiday not mentioned in the Bible, Hanukkah commemorates the victory of the Maccabean Revolt against the Greek rulers of the Land of Israel in the second century B.C.E.
Specifically, the eight-day holiday marks the miracle of the vial of oil that should have sufficed for only one day but that burned for eight, when the Temple was re-sanctified after being profaned by the Greeks.
Like other religions holidays that take place during the darkness of winter, Hanukkah is a festival of lights, with one extra candle being lit each evening until the candelabra is fully illuminated. In religious terms, Hanukkah is a minor holiday, and work is permitted on it, but, perhaps because of its proximity to Christmas, it is celebrated to the hilt among many American Jews, with gifts being exchanged.
Tu Bishvat (a Jewish holiday named for its date – Shvat is the fifth month; tu is a Hebrew acronym for 15) is a Jewish Arbor Day, when trees are planted and which is used, according to the Mishna (Tu Bishvat is not mentioned in the Bible), to determine a plants age for purposes of tithing. Today, the day has a variety of customs associated with it, most memorably the eating of dried fruit.
Next up is Purim (lots), which falls on Adar 14 (Adar 15 in walled cities, including Jerusalem). The day, described in the biblical Book of Esther, marks the salvation of ancient Persian Jews from a plot to wipe them out.
The story transpired in Shushan, the walled capital city of Persia, where, according to the scroll, the plot was only fully foiled on Adar 15. The savior of Purim was Esther, the Jewish queen of King Ahasuerus, and the day is celebrated with reading the book named for her, and observance of a Talmudic commandment to drink until you cannot distinguish between Haman, the evil vizier who planned the genocide, and Mordecai, Esthers wise uncle, who alerted her to the plot.
A month later, on Nisan 15, the all-important Jewish festival of Passover (Pesach in Hebrew) begins. Historically, it is the first of the three festivals, and commemorates the Israelites escape from slavery in Egypt, as described in the Book of Exodus, and all of the miracles associated with that event. (One of those miracles is that in the final one of the 10 Plagues, the angel of death passed over the
homes of the Israelites when it slayed the first-born sons of the Egyptians – hence the name.) It is a celebration of spring and of the rebirth of the Jews as a nation.
Like Sukkot, Pesach lasts seven days (eight outside Israel), with its first and last days being holy days.
During the entire festival, one refrains from eating bread, and by inference, an entire variety of other foods that have the potential to ferment, so as to recall the haste with which the Israelites left Egypt, with not enough time to allow their bread to rise sufficiently. Thats the reason we eat unleavened bread – matzo – both at the seder, the ritual meal observed at the start of the holiday, and throughout the holidays duration.
Seven weeks after the Exodus, Moses received the Torah – that is, the corpus of Jewish law, both written and oral — from God on
Mount Sinai, a momentous event commemorated by Shavuot(weeks), a one-day festival that also marks the spring harvest, when the first fruits were gathered and brought to the Temple as offerings.
Shortly after Pesach, in Israel, several contemporary special days – not strictly holy days — are commemorated: Holocaust Remembrance Day, on Nisan 27; and Memorial Day for the fallen of Israels wars and terror attacks, which is followed immediately by Independence Day, when the state was declared, on Iyyar 4 and 5, respectively.
After that, there remains just Tisha B’Av (9th of Av), the mid-summer fast day that commemorates the destruction of both the First and Second Temples, and a number of other disasters that afflicted the Jews throughout history on this date. There are several other fast days during the course of the Hebrew year; generally, only those who are religiously observant are aware they are taking place, as they do not prevent people from going to work.
The cycle comes to a close and then begins again in the fall.
The above information comes from the HAREETZ website