Tu b'Av: Beginning of the grape harvest
Yom Kippur: End of the grape harvest
(ח) אָמַר רַבָּן שִׁמְעוֹן בֶּן גַּמְלִיאֵל, לֹא הָיוּ יָמִים טוֹבִים לְיִשְׂרָאֵל כַּחֲמִשָּׁה עָשָׂר בְּאָב וּכְיוֹם הַכִּפּוּרִים, שֶׁבָּהֶן בְּנוֹת יְרוּשָׁלַיִם יוֹצְאוֹת בִּכְלֵי לָבָן שְׁאוּלִין, שֶׁלֹּא לְבַיֵּשׁ אֶת מִי שֶׁאֵין לוֹ. כָּל הַכֵּלִים טְעוּנִין טְבִילָה. :
(8) Section one: Rabbi Shimon ben Gamaliel said: There were no days of joy in Israel greater than the fifteenth of Av and Yom Kippur. On these days the daughters of Jerusalem would go out in borrowed white garments in order not to shame any one who had none. All these garments required immersion.
§ The mishna taught that Rabban Shimon ben Gamliel said: There were no days as happy for the Jewish people as the fifteenth of Av and as Yom Kippur. The Gemara asks: Granted, Yom Kippur is a day of joy because it has the elements of pardon and forgiveness, and moreover, it is the day on which the last pair of tablets were given.
שבהן בנות ירושלים כו': ת"ר בת מלך שואלת מבת כהן גדול בת כהן גדול מבת סגן ובת סגן מבת משוח מלחמה ובת משוח מלחמה מבת כהן הדיוט וכל ישראל שואלין זה מזה כדי שלא יתבייש את מי שאין לו:
The mishna taught: As on them the daughters of Jerusalem would go out in white clothes, and on the fifteenth of Av they would go out to the vineyards and dance. The Sages taught this tradition in greater detail: The daughter of the king borrows white garments from the daughter of the High Priest; the daughter of the High Priest borrows from the daughter of the deputy High Priest; the daughter of the deputy High Priest borrows from the daughter of the priest anointed for war, i.e., the priest who would read verses of Torah and address the army as they prepared for battle; the daughter of the priest anointed for war borrows from the daughter of a common priest; and all the Jewish people borrow from each other. Why would they all borrow garments? They did this so as not to embarrass one who did not have her own white garments.
Excerpts from Taanit 31a
Rav Yehuda amar Shmuel: This was the day on which the members of different tribes were permitted to enter one another’s tribe, by intermarriage.
Rav Yosef amar Rav Nachman: The fifteenth of Av was the day on which the tribe of Benjamin was permitted to enter the congregation of the Jewish people.
Rabba bar bar Hana amar Rabbi Yochanan: The fifteenth of Av was the day on which the deaths of the Jews in the wilderness ceased. The entire generation that had left Egypt had passed away.
Ulla: The fifteenth of Av was the day on which King Hoshea, son of Ela, canceled the guards that Jeroboam, son of Nevat, placed on the roads so that the Jews would not ascend to Jerusalem for the pilgrim Festival.
Rav Mattana amar: There was an additional salvation on this day, as it was the day that the slain of Beitar were brought to burial, several years after the battle at Beitar.
Rabba v'Rav Yosef d'amri: The fifteenth of Av was the day on which they stopped chopping down trees for the arrangement of wood that burned on the altar.
Amar Rav Menashye: And they called the fifteenth of Av the day of the breaking of the scythe, as from this date onward no more trees were cut down, and therefore it was a celebration for the trees.
Daf Shevui to Ketubot 62b:4
There are many ironic elements of this tragic story. First of all, his name is Rehumi, which is the Aramaic word for “lover.” But whom does he love—the Torah or his wife? R. Rehumi “regularly” comes home once a year. The day he comes home is Yom Kippur—perhaps in acknowledgement that by staying away he is committing a sin. Maybe he comes home to ask her forgiveness. In the end, her tears kill him. R. Rehumi did not have the ability to truly understand his wife’s pain, and for that he was punished severely.