Nation What is Yom Kippur? How do Jews observe it? And when does the fast start? October 8, 2019 Ashley May and Ryan W. Miller, USA TODAY Comments Off on What is Yom Kippur? How do Jews observe it? And when does the fast start? Yom Kippur is the day of atonement after the Jewish new year, Rosh Hashanah. On this day, Jews ask God for forgiveness for their sins.