Yom Kippur יום כיפור
The tenth of Tishrei — a day of fasting, prayer and forgiveness, set on the day of the second tablets.
Yom Kippur received its meaning in 2449: Moshe came down with the second tablets on the tenth of Tishrei, and the day of forgiveness after the golden calf became the day of forgiveness forever.
In the Temple this was the one day the high priest entered the Holy of Holies — in white linen, with incense, pronouncing the Name. Two goats, one offered and one sent «to Azazel», and a crimson thread that turned white as a sign of pardon. Tractate Yoma describes it minute by minute; the order is recited today in the Avodah service.
After the destruction there remain five prohibitions — food and drink, leather shoes, anointing, washing, marital relations — and twenty-five hours of prayer, from Kol Nidrei to Neilah, when the gates close. The Talmud is firm: the day atones for offences against God, not against another person until you have asked.