Tu B'Av, 15 Av

Tu B'Av falls on the fifteenth of Av, the date this rule records, and its earliest description comes from the Mishnah, the foundational rabbinic legal text, which names it alongside Yom Kippur as one of the two happiest days of the ancient Israelite year, an unexpected pairing of the year's most solemn fast with what was otherwise a minor midsummer date. The Mishnah's own description of the day centers on unmarried young women dancing in the vineyards in borrowed white garments, deliberately unadorned so that wealth would not distinguish one dancer from another, while eligible men looked on and chose partners, a matchmaking custom the text presents as the day's defining practice in the period it describes.

Beyond that early description, the day carries little further explanation in ancient sources and largely receded into a minor, barely observed date across the medieval and early modern periods, without developing the fasting, liturgy or historical narrative that gave other calendar dates their lasting weight. Its modern prominence is a twentieth century development within Israeli culture, where Tu B'Av has been revived and popularized as a romantic holiday broadly comparable to Valentine's Day, a modern reinvention that reaches back to the Mishnah's own vineyard dance for its theme while otherwise having little continuous practice connecting the ancient description to the present day observance.