The Jewish calendar has six fast days, which have different levels of stringency.
The strictest fast, and the only one required by biblical law, is Yom Kippur, the Day of Atonement for sins. On Yom Kippur both eating and drinking are absolutely prohibited for a little more than 24 hours, from sunset on one day until after nightfall the next day. This fast include four additional prohibitions:
- bathing or any washing for pleasure
- applying oil and other pleasurable anointment to the skin
- sexual relations
- leather footwear
Next in stringency is the Ninth of Av (Tisha B'Av), the fast that commemorates the destruction of the First and Second Temples in Jerusalem. This rabbinically-ordained fast is parallel to Yom Kippur in that eating and drinking are prohibited for a little over 24 hours the four additional prohibitions are also proscribed.
"Minor" Fast Days
Three additional “minor” fasts (the 10th of Tevet, the 17th of Tammuz, and Tzom Gedaliah) mark other events connected with the destruction of the Temples. The Fast of Esther falls on the day before Purim and commemorates the fighting between the Jews and their enemies. These fasts are less rigorous: eating and drinking are prohibited but only from before dawn until nightfall, and the other prohibitions do not apply.