|Topics of interest|
The following are all the holidays traditionally observed on the Jewish calendar:
 Biblical holidays
 Rosh Hashanah
1-2 Tishrei - Rosh Ha-Shanah is the Jewish new year and the start of the ten days of forgiveness, in which God judges each person individually according to their deeds, and makes a decree for the following year. The holiday is characterized by the special mitzvah of blowing the shofar. The better people are "inscribed in the Book of Life."
 Yom Kippur (Day of Atonement)
10 Tishrei - Yom Kippur is considered by Jews to be the holiest and most solemn day of the year. Its central theme is atonement and reconciliation. Eating, drinking, bathing, anointing with oil, and marital relations are prohibited. Fasting begins at sundown, and ends after nightfall the following day. Yom Kippur services begin with the prayer known as "Kol Nidrei", which must be recited before sunset.
15-21 Tishrei - Sukkot is a 7-day festival, also known as the Feast of Booths, the Feast of Tabernacles, or just Tabernacles. It is one of the three pilgrimage festivals mentioned in the Bible. The word sukkot is the plural of the Hebrew word sukkah, meaning booth. Jews are commanded to "dwell" in booths during the holiday. This generally means taking meals, but some sleep in the sukkah as well. There are specific rules for constructing a sukkah. The seventh day of the holiday is called Hoshanah Rabbah.
 Simchat Tora
22 (23) Tishrei - Simchat Torah means "rejoicing with the Torah". It actually refers to a special ceremony which takes place on the holiday of Shemini Atzeret. This holiday immediately follows the conclusion of the holiday of Sukkot. In Israel, Shemini Atzeret is one day long and includes the celebration of Simchat Torah. Outside Israel, Shemini Atzeret is two days long and Simchat Torah is observed on the second day, which is often referred to by the name of the ceremony. The last portion of the Torah is read, completing the annual cycle, followed by the first chapter of Genesis. In keeping with the theme of continuing the cycle, the first chapter from the Book of Joshua, which takes place immediately following the events at the end of the Torah, is also read. Services are especially joyous, and all attendees, young and old, are involved.
 Pesach (Passover)
14-22 Nisan - Pesach (Passover) commemorates the liberation of the Israelite slaves from Egypt. No leavened food is eaten during the week of Pesach, in commemoration of the fact that the Jews left Egypt so quickly that their bread did not have enough time to rise. Except for matzo, no wheat is allowed; a loophole sort of exists in that if it was once matzo, it's still considered matzo, so many matzos are ground up and the 'flour' is turned into various foods, the result being the paradox where some people eat more 'breads' on Passover than not on Passover. Millet, rye, spelt and barley are also forbidden. Ashkenazim (German Jews) also ban beans or any other grain that could be theoretically used to make bread, while Sephardim (most other Jews) do not.
6, 7 Sivan - Shavuot, The Feast of Weeks is one of the three pilgrim festivals (Shalosh regalim) ordained in the Torah, Shavuot marks the end of the counting of the Omer, the period between Passover and Shavuot. According to Rabbinic tradition, the Ten Commandments were given on this day. During this holiday the Torah portion containing the Ten Commandments is read in the synagogue, and the biblical Book of Ruth is read as well. It is traditional to eat dairy meals during Shavuot, especially ice cream.
Every seventh day - Jewish law accords the Sabbath the status of a holiday. Jews celebrate a Shabbat (Yiddish:Shabbos), a day of rest, on the seventh day of each week. Jewish law defines a day as ending at nightfall, which is when the next day then begins. Thus, Shabbat begins at sundown Friday night, and ends at nightfall Saturday night. Traditionally meals eaten during Shabbat are special, Jewish households tend to spend as much as they can afford, families bond and special prayers are said and there are special ceremonies. Among Orthodox Jews most cooking must be finished before sunset on Friday evening and in the past slow cookers, today cookers with timers are used to get the food ready on time. 
In many ways Jewish law gives Shabbat the status of being the most important holy day in the Jewish calendar.
- It is the first holiday mentioned in the Tanakh (Hebrew Bible), and God was the first one to observe it; as a result, the rules of Shabbat actually overrule the rules of other holidays (except Yom Kippur, which is called "the Shabbat of Shabbats").
- The Jewish services treats the Sabbath as a bride and queen (along with God the groom).
- The Torah portion on the Sabbath has more sections of Torah readings than on Yom Kippur, the most of any Jewish holiday.
- There is a tradition that the Messiah will come if every Jew observes the Sabbath twice in a row.
- Walter Sobchak doesn't roll on Shabbos.
- Although Jews do not believe Gentiles are bound by any of the commandments in the Torah, keeping the Sabbath is the only one specifically reserved for Jews. That is to say, non-Jews are free to observe any of the other commandments if they so choose, but Jews believe the Sabbath was specifically given to them by God. In fact, someone wishing to convert to Judaism is required to take at least one action to break the Sabbath each week until the process is completed.
 Apocryphal/Non-traditional holidays
Each of these events occurred at some point after the 597, 587, and 582 B. C. E. expulsions, which together launched the first diaspora since the birth of fully monotheistic Judaism (that having been created a few years earlier in Babylon in an expulsion that started in 604). As a result of the scattering of the Jews (some went as far west as Morocco, and others as far east as India), not all Jews even knew about events like Hanukkah, which occurred in 150 B. C. E. (heck, the first Jews to arrive in Italy did so in 200 B. C. E.), so celebrating Hanukkah has not been nearly as long a tradition for many Jewish communities around the world as it has been for others.
25 Kislev - 2, 3 Tevet - The story of Hanukkah is preserved in the books of the First and Second Maccabees. These books are not part of the modern Tanakh (Hebrew Bible); they are considered apocryphal books instead. The miracle of the one-day supply of oil miraculously lasting eight days is first described in the Talmud. Long story short, Greeks
steamroll into conquer Israel and many Jews become Hellenized. Judah Maccabe leads a revolt against the Hellenized Jews Greeks and kicks ass. However, the temple only had enough kosher oil for one day's worth of flames, and it'd be eight days before more kosher oil could be made, but the oil lasted the whole eight days. No one noticed if there were seven days of non kosher oil missing during this time.
The tradition of giving presents on Hanukkah is recent enough that the theory that it was created to take advantage of Christmas sales is not unreasonable.
 Tu Bishvat
15 Shevat - Tu Bishvat is the new year for trees. According to the Mishnah, it marks the day from which fruit tithes are counted each year, and marks the time-point from which the Biblical prohibition on eating the first three years of fruit and the requirement to bring the fourth year fruit to the Temple in Jerusalem were counted. In modern times, it is celebrated by eating various fruits and nuts associated with the Land of Israel, and by planting new trees.
14 Adar (14 Adar 2 leap year) - Purim commemorates the events that took place in the Book of Esther. It is celebrated by reading or acting out the story of Esther, by dressing up in costume, by making disparaging noises at every mention of Haman (the antagonist)'s name, by giving charity to someone who is poor, by eating the purim meal and by getting absolutely smashed. This is by far more fun than Hanukkah. Note that in Jerusalem, Purim is celebrated one day later than in the rest of the world, on 15 Adar (or 15 Adar 2 in a leap year) and is formally known Shushan Purim.
 Tisha B'Av
Fast holiday, commemorates the destruction of the First and Second Temples in Jerusalem by the Romans, which according to tradition happened on the same day in the Hebrew Calendar, 9 Av, as well as three other tragedies (the revolt of the spies in Numbers 13-14, the putting down of the Bar Kochba revolt, and the plowing of the site of the Second Temple following its earlier destruction.) Many Jews also use the holiday to commemorate more recent calamities which occurred on or around 9 Av, such as the Jews' expulsion from England, France, and Spain, the formal approval of the Final Solution, and the mass deportation of Jews from the Warsaw Ghetto to Treblinka. The dates for many of these more recent events were deliberately chosen by their perpetrators to be on or around Tisha B'Av, presumably in a further attempt to spite the Jews. There is speculation that the AMIA bombing, which occurred on 18 July 1994/10 Av 5754 and targeted a Jewish Community Center in Buenos Aires, was also deliberately planned to coincide with the holiday.
 Modern holidays
In the 20th century most Jews added three holidays to their liturgical calendar. While several of these are technically Israeli holidays, many Jewish groups have embraced them as well.
 Yom HaShoah
Literally "Day of the Storm" (though "Shoah" is the commonly accepted Hebrew term for the Holocaust) it is also known in English as Holocaust Remembrance Day. It is observed on the Hebrew calendar's anniversary of the Warsaw Ghetto Uprising. In Israel air raid sirens are sounded and people are expected to come to a standstill to mark a national moment of silence in honor of the victims.
 Yom HaZikaron
The Israeli equivalent to Memorial Day, except without the grilling and three day weekend, and with things that actually honor their soldiers.
 Yom Ha'atzmaut
Israeli independence day, this celebrates the foundation of the modern state of Israel. Takes place the day after Yom HaZikaron (to remember, that the foundation and continued existence of the state was and is payed with the blood of its soldiers).
 Yom Yerushalayim
Honors, from the Israeli perspective, the re-unification of Jerusalem after the end of the Six-Day War.
- ↑  
- ↑ When Yom Kippur falls on Shabbat, the text of the Torah reading is the same but is divided up into more sections.
- ↑ This is because they were written in Greek, not Hebrew, and therefore were not included in the traditional Masoretic text. They do, however, appear in the Septuagint, and are therefore considered canon by the Roman Catholic and Orthodox communities.
- ↑ This apparently nonsensical requirement makes sense to a farming society. Typically with orchards, the farmer will clip the fruiting bodies of saplings so that the fruit tree will not waste energy on fruit but instead grow faster. What starts off as tribal knowledge is codified into "shut up and just do it or you'll be smited repeatedly for eternity".