Yom Kippur
Also known as the Day of Atonement, this was the most solemn, holy day of all the Israelite feasts and festivals and is still observed each year during September-October based on the specific Hebrew calendar day (Lev 16:1-34, 23:27,28). An elaborate ritual was performed to symbolically atone or make amends for the sins of the people. Only the high priest was permitted to enter the Most Holy Place (Holy of Holies) of the tabernacle (and later the temple), and only once per year, to offer sacrifices on behalf of the people. In 70 AD the Romans destroyed the temple containing the only God-authorized altar for burnt sacrifices; thus the sacrifices have ceased.
See also: atonement, feasts, tabernacle, temple.