Yom Kippur, the Day of Atonement, falls on the Hebrew calendar date of 10 Tishrei.
Here are the coinciding secular dates for upcoming years:
2008: October 9
2009: September 28
2010: September 18
2011: October 8
2012: September 26
2013: September 14
2014: October 4
2015: September 23
The Jewish calendar date begins at sundown of the night beforehand. Thus all holiday observances begin the night before the dates listed. Jewish calendar dates conclude at nightfall.
Yom Kippur follows Rosh Hashanah, the Jewish New Year.