Fourth ecclesiastical and tenth civil month of the Hebrew calendar. It consists of twenty-nine days, and corresponds to part of June and part of July. During the last years of the Second Temple the 14th of Tammuz was declared a feast-day in commemoration of a victory gained by the Pharisees over the Sadducees in a dispute regarding the interpretation of the Law (Ta'an. iv. 6). The 17th of Tammuz is the public fast-day called "Shib'ah 'Asar be-Tammuz," in commemoration of the breaking down of the walls of Jerusalem by Nebuchadnezzar. As stated in Jer. xxxix. 2, this catastrophe occurred on the 9th day of the month; the 17th was selected because, during the siege of Jerusalem by Titus, a similar catastrophe happened on that day (Ta'an. 26a; Shulḥan 'Aruk, Oraḣ Ḥayyim, 549).
According to the Megillat Ta'anit (iv. 6), four other calamities had overtaken the people of Israel on the 17th: the breaking of the tables of the Law by Moses, the cessation of the perpetual offering, the burning of the Torah and the erection of an idol in the sanctuary, by Apostomus (comp. Josephus, "Ant." xx. 5, § 4; idem, "B. J." ii. 12, § 2), and the discontinuance of the sacrifices. With the 17th begin the three weeks of mourning over the destruction of Jerusalem, which end with the 9th of Ab. During this period it is forbidden to celebrate marriages, to cut the hair, to bathe, etc. (Shulḥan 'Aruk, Oraḥ Ḥayyim, 551). The pious fast every day during these three weeks (ib.). The 27th of Tammuz is the anniversary of the burning of the tanna Ḥanina ben Teradion during the Hadrianic persecutions (additions to Megillat Ta'anit, ed. Neubauer, in "M. J. C." ii. 24).