Dear Doves:

There are no holy days as happy for the Jews as Tu B'Av and Yom Kippur.
Is there a prophetic meaning?
I think that they're connected to the tablets of Moses.
We know that the first and second tablet represent Flesh and Spirit.
Moses went up to God on Shavout, and the first tablet was broken on Tammuz 17.
Tu B'Av is observed after 7 days from Tisha B'Av which is 3 weeks from Tammuz 17.
The second tablet was completed on Yom Kippur when Moses came down with a radiant face.
Thus it's possible that Tu B'Av is designed for the Firstfruits and Yom Kippur is for the second departure.
It's just my opinion.
Maranatha!