Christian observance of Yom Kippur
Christian observances of Yom Kippur occur when a Christian-style Day of Atonement models itself on the Jewish holiday of Yom Kippur.
Roman Catholicism
In the Roman calendar still observed by Traditionalist Catholics, the Michaelmas Ember days are penitential days inspired by the Jewish solemnities of the “seventh month,” Tishrei, especially Yom Kippur. Those days' first Lesson focuses on the Old Covenant’s Day of Atonement and the fast of the seventh month.Sabbatarian churches
As observed by the Living Church of God and United Church of God:
The Christian Day of Atonement is based on the English translation of the Jewish Holy day Yom Kippur. The day is commemorated with a 25-hour fast by Jews, but normally a 24-hour fast by Christians who observe it. While not observed by the mainstream of professing Christianity, the Christian groups that do observe it usually refer to it as the Day of Atonement...
Generally, the Sacred Name Movement and groups reject Easter and Christmas as pagan in origin and observe the holy days of Leviticus 23 such as Yom Kippur, as well as Passover and the Feast of Weeks.