The 15th of Av is a most mysterious day. A search of the Shulchan Aruch (Code of Jewish Law) reveals no observances or customs for this date, except for the instruction that the tachanun(confession of sins) and similar portions should be omitted from the daily prayers (as is the case with all festive dates), and that one should increase one’s study of Torah, since the nights are begining to grow longer, and “the night was created for study.”
The Talmud tells us that many years ago the “daughters of Jerusalem would go dance in the vineyards” on the 15th of Av, and “whoever did not have a wife would go there” to find himself a bride. And the Talmud considers this the greatest festival of the year, with Yom Kippur (!) a close second!
As the “full moon” of the month of Av, it is the festival of the future Redemption, marking the end of the tragedy that marred the first part of the month. Until this day, we held siyumim and gave charity each day to mitigate our sadness and hasten the Redemption. But on the 15th of Av, this is no longer. Forty-five days before Rosh Hashanah , this is also the first day on which we begin to wish each other a ketivah vachatimah tovah, to be signed and sealed for a good year.