Question: When is Yom Kippur 2010?
Yom Kippur (the Day of Atonement) is one of two Jewish High Holy Days. The first High Holy Day is Rosh Hashanah (the Jewish New Year). Yom Kippur falls ten days after Rosh Hashanah on the 10th of Tishrei.
Answer: Yom Kippur begins at sundown on September 17th, 2010 (Friday). It ends at sundown on September 18th, 2010 (Saturday).

