When did the Day of Atonement begin?
The Day of Atonement began in the days shortly after Israel came out of Egypt, the same as all the other Feast Days, including Passover, First Fruits, and Unleavened Bread. It was a Fall feast, later called Yom Kippur in English.
Les explains that the Day of Atonement was begun back in the days shortly after the Israelites came out of Egypt, just like all the other Feast Days, such as Passover, First Fruits, and Unleavened Bread. He notes that Passover was the Spring feast, the memorial of the Night of the Passover in Egypt when the death angel flew over and they were protected by the blood. But Atonement was in the Fall, and its present English name is Yom Kippur, which is a far better definition. He also points out that the word 'Atonement' is really a misnomer, because there was no atonement—animal blood could not take away sin. The word can be split into 'At-one-ment,' which is a good definition.