Chabad.org 18 Tisha B'Av Facts Every Jew Should Know By Menachem Posner

1.Tisha B’Av, the 9th day of the month of Av (Aug. 10-11, 2019), is the saddest day on the Jewish calendar. Referred to by the prophet as “the fourth [month] fast,”1 it is second in severity only to Yom Kippur, which is mandated in the Torah.