1911 Encyclopædia Britannica/Ab
AB, the fifth month of the ecclesiastical and the eleventh of the civil year of the Jews. It approximately corresponds to the period of the 15th of July to the 15th of August. The word is of Babylonian origin, adopted by the Jews with other calendar names after the Babylonian exile. Tradition ascribes the death of Aaron to the first day of Ab. On the ninth is kept the Fast of Ab, or the Black Fast, to bewail the destruction of the first temple by Nebuchadrezzar (586 B.C.) and of the second by Titus (A.D. 70).