Jews for Jesus: Yom Kippur, the Day of Atonement, is the holiest and most somber day of the Jewish year. Yom Kippur concludes the Ten Days of Awe that begin with Rosh Hashanah (the Jewish New Year). Like Rosh Hashanah, Yom Kippur is a prospective holiday, when we prepare for the year ahead through fasting, penitence and confession.