Also known as the "Day of Atonement" Yom Kippur is considered the most sacred day in the Jewish calendar by observant Jews. In a manner similar to Christians and church attendance for Easter, even many Jewish people who are not deeply religious will find their way to Temple on this very special day.
Yom Kippur is observed by many sects of modern Judaism with a 24 hour fast and prohibitions from work. In many cities in the northeast United States public schools and some colleges and universities are closed for this Jewish holiday. The service is a somber and introspective occassion.