Aw (Hebrew אָב, from Akkadian abu ) is the eleventh month of the ecclesiastical year and the fifth of the civil year in the Jewish calendar. He has 30 days and falls in the Gregorian calendar mostly in the period of July and August.
The month name is attributed to the calendar of the Chaldeans, which was from the first month of the year. As the only month that is not mentioned in the Bible, he first appears around the 3rd century in the Talmud. The Jews took it over, like all other names of months, after the Babylonian exile in their calendar.
In Judaism, Aw is considered the most fateful month because each on the 9th day of the month twice ( 586 BC to 70 AD), the temple in Jerusalem, as well as 135 AD, the last stronghold of the Jewish population under Bar - Kochba had been against the Roman occupation, the city Bethar destroyed. Furthermore, all Jews were expelled from England for nearly four centuries 9th of Av 1290.
The 15th of Av is true because of numerous historical events as positive rejoicing. Both the 9th and the 15th of Av are holidays.