From sundown on Saturday, July 24 to nightfall on Sunday, July 25, 2100. 18 Tamuz 5860 · צום י״ז בתמוז The Seventeenth of Tammuz (Biblical Hebrew: שִׁבְעָה עָשָׂר בְּתַמּוּז, Modern: Shiv'á Asár beTammúz, Tiberian (SBL): Šib̲ʿāʿāśār bəṯammuz) is a Jewish fast day commemorating the breach of the walls of Jerusalem before the destruction of the Second Temple. It falls on the 17th day of the Hebrew month of Tammuz, the fourth month, and marks the beginning of The Three Weeks, a mourning period leading up to Tisha B'Av. The day also traditionally commemorates the destruction of the two tablets of the Ten Commandments and other historical calamities that befell the Jewish people on the same date. Wiki link Dates: Hebcal.com (CC BY 4.0), Diaspora schedule. Text: Wikipedia (CC BY-SA).