It has also became a day of general mourning for other major disasters that have befallen the Jewish people, from the Edict of Expulsion from England in 1290 to the mass deportation of Jews from the Warsaw Ghetto.
Tisha B’Av, the ninth day of the month of Av (which month coincides with July and/or August), is the major day of communal mourning in the Jewish calendar. Although a large number of disasters are said to have befallen the Jews on this day, the major commemoration is of the destruction of the First and Second Temples in Jerusalem in 586 B.C.E. and 70 C.E., respectively. Central to the observance of this day is fasting.
Ideas & Beliefs
Although the exact date of the destruction of each of the Temples–the ancient centers of Jewish life and practice–are unknown, tradition dates the events to Tisha B’Av. Indeed, the rabbis of the Talmudic age made the claim that God ordained this day as a day of disaster as punishment for the lack of faith evidenced by the Israelites during their desert wanderings after the exodus from Egypt . During the course of the centuries, a number of tragedies have clustered around this day, from the expulsions of the Jews from England and Spain to more localized disasters. Tisha B’Av is therefore observed as a day of communal mourning, which is expressed through fasting and the abstention from pleasurable activities and extraneous diversions. A whole literature of dirges appropriate to this day of mourning, beginning with the biblical Book of Lamentations on the destruction of the First Temple, has been created to serve the needs of the Jewish community at this time.
Material excerpted from http://www.myjewishlearning.com/.