Tu B'Av falls between mid-July and mid-August. The name literally means "the 15th (day) of (the Hebrew month) Av", and was marked as an ancient holiday of nature and agriculture in the land of Israel, celebrated all over Israel at the same time. Tu B'Av marks the beginning of the end of summer, when the sun's strength begins to decrease, the hours of darkness increase, and the rainy season is no longer a distant dream. Throughout Israel, Tu B'Av is marked by an increase in dew and moisture, which induces the flowering of the white squill and stimulates the olives to begin to fill with oil.
According to the Mishna (Tractate Ta'anit 4,8), Tu B'Av was one of two days during the year on which young single women would dance in the olive groves in order to meet potential suitors. The women would wear borrowed white clothes "in order not to embarrass whoever did not own any." The white color reflected the ubiquitous blossoming white squill so common in the Israeli landscape at this time of year.
The Sages taught several reasons why Tu B'Av was such joyous day:
- On Tu B'Av the law restricting women to marry within her tribe (in order to keep property within the tribe) was lifted for that day only.
- Centuries later, on Tu B'Av, the restriction on intermarriage among the tribes was abolished.
- On or about Tu B'Av young olive fruit start filling with oil, a process that reaches its peak months later in late October. In Arab, as in local Jewish folklore, the day was also called "olive day."
Tu B'Av comes two months before the end of the ingathering on Sukkot. The grapes, olives, and dates are yet to be harvested and an even longer period remains before the plowing of the fields for sowing with the first rains of winter. It was a brief window of relatively free time from fieldwork. As such, it was an ideal opportunity for those who were not yet married to take a break in the yearly cycle to enjoy meeting potential spouses in the olive groves, traditional Judaism's ancient equivalent of "Valentine's Day".
For more information on the history and agricultural connections of Tu B'Av, please see the book "Nature in Our Biblical Heritage" by the founder of Neot Kedumim, Nogah Hareuveni.