Tisha B'Av
Tisha B'Av תשעה באב means the ninth day of the month of Av, which is a month in the lunar calendar used for purposes of Jewish holidays, etc.This is a fast day, that commemorates two of the saddest days in Jewish history -- the destruction of the first Temple originially built by King Solomon,(see Solomon's Temple), and the destruction of the Second Temple. Those two events occurred about 556 years apart, but both in the same month, Av, and both on the ninth day.
On this day both the First and Second Temples were destroyed (587 BC and 70 AD). On this day in 1290, King Edward I signed the edict compelling the Jews to leave England. The Jewish expulsion from Spain in 1492 also occurred on this day.
The Jews commemorates Tisha B'Av by a fast (a day without eating or drinking) and reading the scroll of 'Ekhah, or Lamentations, in synagogue.
See also: Jewish holidays.