Av is the eleventh month of the civil year and the fifth month of the ecclesiastical year on the Hebrew calendar. It is a month of 30 days, and usually occurs in July–August on the Gregorian calendar.
Francesco Hayez, The Second Temple in flames, 1867. The 9th of Av, Tisha B'Av, is a fast commemorating what has been called the saddest day in Jewish history, which is when the Holy Temple was set aflame.