Yom Kippur is probably the most important holiday of the Jewish year. Many Jews who do not observe any other Jewish custom will refrain from work, fast and/or attend synagogue services on this day. Yom Kippur occurs on the 10th day of Tishri. The holiday is instituted at Leviticus 23:26 et seq. The name Yom Kippur means Day of Atonement, and that pretty much explains what the holiday is. It is a day set aside to afflict the soul, to atone for the sins of the past year. In Days of Awe, I mentioned the books in which G-d inscribes all of our names.