Av

Av is the fifth month of the Hebrew year, falling in high summer, roughly July to August, and aligned in tradition with the sign of Leo. It counts thirty days. Its ninth day, Tisha B'Av, is the major fast of mourning in the Jewish year, commemorating the destruction of both the First and Second Temples and other calamities, the culmination of the three weeks that began in Tammuz. Yet the month turns toward consolation: the fifteenth, Tu B'Av, is a minor festival associated with love and joy. The name is often given more fully as Menachem Av, Av the comforter. The Hebrew calendar is lunisolar, kept in step with the solar year by an added leap month. These are the observances of the Jewish calendar tradition, in which Av moves from deepest mourning toward comfort.

Av holds Tisha B'Av, the ninth of Av, the most solemn fast day of the Hebrew calendar after Yom Kippur, traditionally marking the destruction of both the First Temple by Babylon in 586 BCE and the Second Temple by Rome in 70 CE, along with a cluster of later catastrophes Jewish tradition has attached to the same date, including the 1290 expulsion of Jews from England and the 1492 expulsion from Spain. The fast closes the three-week mourning period, Bein HaMetzarim, begun on the seventeenth of Tammuz the month before. Yet the fifteenth of Av, Tu B'Av, falling in the same month, is treated in the Mishnah as one of the most joyous days of the year, traditionally associated with matchmaking and marriage, a sharp contrast within a single month the tradition itself does not attempt to resolve into a single unified theme.

The name comes from the Akkadian Abu, one of the Babylonian month names adopted wholesale into Hebrew usage. The month runs a fixed 30 days in every year.

The month names are Babylonian. Twelve of them are the Akkadian month names taken into Hebrew during and after the exile, and the biblical books of the return use them freely while the earlier books generally number the months or use a small set of older Canaanite names. The atlas records the borrowing rather than presenting the names as native, because it is one of the clearest visible marks the exile left on Jewish practice.

The Jewish calendar as now kept is calculated rather than observed. Month lengths are fixed by rule except for Cheshvan and Kislev, which absorb the adjustment and may run 29 or 30 days, and a thirteenth month is added in seven years out of nineteen on a fixed cycle so that Passover stays in the spring. A further set of rules, the postponements, shifts Rosh Hashanah off certain weekdays, which is why the year has six possible lengths rather than two.

Av contains the ninth of the month, Tisha B'Av, the fast that commemorates the destruction of both Temples and to which later tradition attached other calamities as well. It is the principal day of mourning in the Jewish year and the only full fast besides Yom Kippur.