Yom Kippur is the holiest day of the Jewish year. 

It's the day of atonement after the Jewish new year, Rosh Hashanah. On this day, Jews ask God for forgiveness for their sins to secure their fate. It's also known as the Sabbath of Sabbaths.

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It begins Friday evening and ends Saturday evening. (Yom Kippur usually falls in September or October each year.) More than half of Jews will observe the holiday by fasting, according to a Pew Research Center survey. Some will avoid working, wearing leather shoes, applying makeup or lotion, washing or bathing and having sex.

During this time, Jews attend worship services where the machzor, a prayer book used during holy days, is read and specific prayers are recited. At the end of the services, a shofar or ram's horn is blown to signal the end of Yom Kippur. Then, Jews are able to feast, breaking the fast.

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Jews believe the first Yom Kippur occurred after God gave Moses the Ten Commandments at Mount Sinai. When Moses came down from the mountain, he found the Israelites worshiping a gold idol calf. After they atoned for their sin, God forgave them and offered Moses a second set of tablets. 

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