Yom Kippur, the Day of Atonement, is obsereved on the Jewish calendar date of 10 Tishrei.
Yom Kippur 2016 is observed from sunset of Tuesday, October 11, 2016 through nightfall of Wednesday, October 12, 2016.
Here are the dates for Yom Kippur in upcoming years:
2017: September 29-30
2018: September 18-19
2019: October 8-9
2020: September 27-28
Note: The Jewish calendar date begins at sundown of the night beforehand. Thus all Yom Kippur observances begin at sundown on the first secular date listed, and conclude the following day at nightfall.