A fast day is a period of time in which a person doesn't eat, but not because they're not hungry. Why it's called a fast day, I'll never understand. I think it should be called a Slow Day, because it always seems as if the day goes by so.o.o.o slowly. But that's just my own opinion.

There are different types of fast days. Some are to commemorate a sad event or tragedy in Jewish history. Others are simply to put us in the mood to repent.

Everyone knows the Fast Day of Yom Kippur, - (The Day of Atonement), the purpose of which is Tshuva (repentance). Yom Kippur, begins on the eve of the tenth of Tishrei. That's when the fast begins too. It's a big one. twenty-five+ hours!

Yom Kippur is the climax to a month of soul searching. Beginning on Rosh Chodesh Elul, we say Selichot, (prayers of repentence), and blow the shofar (ram's horn) as a sign that the day of judgement is right around the corner. Thirty days later, Rosh Hashana, the two-day Jewish New Year, is celebrated with a prayer-fest that urges Hashem to forgive us our sins and grant us a sweet new year. Just in case you haven't been convincing enough, you've got the next ten days to show Hashem you mean it. A combination of Tshuva (repentance), tefilah (prayer) and tzedakah (charity) is the prescribed medicine to ward off a bad decree.

THE
FOUR
FAST
DAYS

Besides Yom Kippur, The Talmud (Tractate Rosh Hashana 18b, see also Beit Yosef Orach Chaim 549) discusses 4 Fast Days that commemorate the destruction of the First and Second Temples, and the exile of the Jewish People from their homeland, Eretz Yisroel.

These 4 fast days are:

1)   TZOM (THE FAST [OF]) GEDALIA - 3^rd of Tishrei

Tzom Gedalia, was instituted by the Rabbis to commemorate the assassination of the Jewish governor of Judah, appointed by Nebuchadnezzar. This critical event was the final blow to the hopes that the Jewish state would survive the Babylonian domination and led to the destruction of the first commonwealth.

2)   ASARA B'TEVET (Tenth of Tevet)

Asara B'Tevet, marks the beginning of the siege of Yerushalayim, during the reign of Nebuchadnezzar, that resulted in the destruction of the First Bait Hamikdash.

Today, Asara B'Tevet has an added meaning. The day is alternatively known as Yom Ha-Kaddish Ha-Klali. It is the memorial day for those Jews who died during the Holocaust whose day of death (Yahrzeit) is unknown, and for those Holocaust victims for whom there were no living survivors to recite the Kaddish. On this date, Kaddish is recited for these souls.

Shiva Asar B'Tamuz, the date when the walls of Yerushalayim were breached, and other tragic events in Jewish history occured.

Tisha B'Av - The saddest day in the Jewish Calendar, recalls the destruction of the First and Second Temples. Later traditions connect the Fast of Av with subsequent tragic events in Jewish history.

OTHER
FAST
DAYS

1)   TA'ANIT (THE FAST [OF]) ESTHER - 13^th of Adar

Ta'anit Esther is observed on the day before Purim, Adar 13, (see Esther 9:31). The Fast of Esther gives us a different perspective on fasting. Sure, it commemorates a terrible day in Jewish history, but it is not a sad day in of itself. In fact, it is a day that leads up to the happiest holiday of the year! In this case, the fast adds to the joy of Purim and makes us even more aware of Hashem's hand in the destruction of Haman.

The Fast of Esther, which begins on the morning of Adar 13, commemorates the three days that Esther fasted before approaching King Achashverosh on behalf of the Jewish people. It is also the anniversary of the day that the Jews fought against their enemies throughout the Persian empire.

1)   TA'ANIT (THE FAST [OF]) BECHORIM - 14^th of Nisan

Ta'anit Bechorim, (The Fast of the First Born) takes place on the 14^th of Nissan, the day before Pesach (Passover). This Fast is observed only by firstborn males. The fast commemorates the fact that Jewish first-born males were saved from the plague of the firstborn in Mitzrayim (Egypt).

All other fasts last from dawn till nightfall. For those who don't fast well, it is good to know that if you wake up before dawn, you can eat breakfast before the fast begins. There is a great deal of leniency in these fasts for people who have medical conditions or other difficulties fasting.

With the exception of Yom Kippur, which is observed even if it falls on Shabbat, if the specified date of a fast falls on Shabbat, the date of the fast is moved to Sunday. Except for Ta'anit Esther. If Adar 13 falls on a Friday or Shabbat, Ta'anit Esther is moved to the preceding Thursday, because it cannot be moved forward a day or it will fall on Purim.

Besides these fasts, individuals and communities have fasted for various religious reasons, especially to avert or terminate calamity. Such fasting, is linked to prayer and Tshuva. 

Public fasts have been proclaimed to avert a public disaster, e.g. upon going to war, or upon a threat of annihilation, famine, oppression, or divine punishment.

Private fasts include that of a bride and groom on the day of their marriage, a fast following a bad dream, or on the day of the death of a close relative (yahrzeit). Certain righteous people take on a three-day fasting cycle of Monday-Thursday-Monday after the festive seasons of Pesach and Sukkot.

(Tzom Gedaliah) Fast of Gedaliah - Tishrei 3

Yom Kippur (Day of Atonement) - Tishrei 10

Asara B'Tevet (Tenth of Tevet)  - Tevet 10

Ta'anit Esther (Fast of Esther) - Adar 13

Ta'anit Bechorim(Fast of the First Born) - Nissan 14

Shiva Asar B'Tamuz (17th of Tamuz) - Tamuz 17

Tisha B'Av (The Ninth of Av) - Av 9