Rabbi Yaakov ben Meir Tam, known as the "Rabbenu Tam," was one of Rashi's illustrious grandsons. During the Second Crusade, on the second day of the holiday of Shavuot, the Crusaders entered his hometown of Ramerupt, and pillaged and massacred many Jews.
They broke into Rabbenu Tam's house, plundered all his wealth, and seriously wounded Rabbenu Tam. On the next day, the 8th of Sivan, Rabbenu Tam escaped Rameru and the clutches of the Crusaders.
Two years later he completed his famous treatise on Jewish ritual and ethics, Sefer Hayashar.
The day following a festival is called Isru Chag ("tied to the festival"). Tachnun (confession of sins) and similar prayers are omitted through the 12th of Sivan.
On Isru Chag, It is customary to hold a kinus Torah, a public gathering in which Torah thoughts are shared and discussed.
Yom Kippur is a day of forgiveness for those who return.
But then, every day is a day of forgiveness for those who return.
Yet Yom Kippur is an entirely different story.
Because on any other day when a soul returns, her misdeeds are discarded.
On Yom Kippur, when a soul returns, she is held in tight embrace.
Within the fire of that embrace, there never were any misdeeds. There is only oneness, peace, and eternal love.