Tu B'Av, the fifteenth of Av, is a minor but ancient day of joy that falls just six days after the mourning of Tisha B'Av, at the full moon. The Mishnah preserves a striking memory of it: it says there were no days as joyous for Israel as the fifteenth of Av and Yom Kippur, on which the daughters of Jerusalem would go out in borrowed white garments, so that none should be shamed by poverty, and dance in the vineyards, where matches were made. Several other happy events in the rabbinic calendar are attached to the day.
For most of Jewish history Tu B'Av had little liturgical content beyond the omission of penitential prayers, and it nearly disappeared as an observance. In the modern State of Israel it has been revived, largely in a secular form, as a day of love and romance, sometimes called a Jewish counterpart to Valentine's Day, marked by weddings, festivals and celebrations of relationships. It is a clear example of an ancient festival, once tied to the agricultural and marriage customs of a vanished society, being given new life and a new meaning by a living culture, and its placement so soon after the year's saddest day gives it, in the tradition, the character of consolation.