Yom Kippur, the Jewish Day of Atonement, is observed in 2012 from sundown Sept. 25 to nightfall Sept. 26. The Hebrew date for Yom Kippur is 9-10 Tishrei 5773.

The Day of Atonement -- also known as the Sabbath of Sabbaths -- is the most important day of the Jewish year. More people go to temple on Yom Kippur than any other holiday.

Yom Kippur marks the end of the Days of Awe, a 10-day period of teshuvah (literally "return," commonly understood as repentance) that begins with Rosh Hashanah, the Jewish New Year.

During the Days of Awe, Jews seeks forgiveness from friends, family and co-workers, a process that begins with Tashlich, the symbolic casting off of sins that is traditionally observed on the afternoon of Rosh Hashanah by throwing bread into a body of water. On Yom Kippur, Jews attempt to mend their relationships with God. This is done partly by reciting the Vidui, a public confession of sins.

The holiday has the most extensive prayer schedule of the Hebrew calendar and arduous abstinence from food, drink, animal-based clothing and sexual intimacy. Communal prayers for Yom Kippur begin with Kol Nidre, a legal document that is hauntingly chanted and emotionally charged. The Book of Jonah is read during the afternoon prayer service on Yom Kippur day. The Day of Atonement is the only Jewish holiday that includes a fifth prayer service, called Ne'ilah, which is a final plea of repentance before the gates of heaven are said to close. The Ne'ilah service precedes the shofar blowing and the end of the fast.

Though Yom Kippur is characterized by fasting and prayers of repentance, it is actually considered the most joyous day of the Jewish year because it commemorates God's forgiveness of the sin of the Golden Calf, and is considered a time to start anew spiritually.

Please join us throughout the Jewish High Holidays, on the HuffPost Religion live-blog, updated daily with spiritual reflections, blogs, photos, videos and verses. Tell us your story.

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  • A young Jewish boy blows the shofar horn along the beach in the coastal city of Ashdod, during the ritual of Tashlich on September 29, 2011. Jews traditionally walk to the nearest water source to hold the Tashlich prayer, in which they empty their pockets and throw the previous years "sins" into the water, ahead of Yom Kippur, or the Day of Atonement. (JACK GUEZ/AFP/Getty Images)

  • David Barkley of Mount Airy, Maryland, and a supporter of Israel, blows a shofar outside the White House in Washington, DC, May 20, 2011, after US President Barack Obama met with Israeli Prime Minister Benjamin Netanyahu in the Oval Office. Obama announced on Thursday in his long-awaited speech on the 'Arab Spring' revolts that territorial lines in place before the 1967 Arab-Israeli war should be the basis for a peace deal, a move Netanyahu has long opposed. (SAUL LOEB/AFP/Getty Images)

  • U.S. pop star Paul Simon receives a ''Shofar'' following his press conference in Tel Aviv, on July 20, 2011. (JACK GUEZ/AFP/Getty Images)

  • An Ultra Orthodox Jewish man blows the Shofar (ram's horn) as he prays among others at the renovated Tomb of Joseph, a biblical figure from the book of Genesis, in the northern Palestinian West Bank city of Nablus, on November 4, 2010 as some 1000 religious Jews were allowed by the Israeli army to enter the Palestinian territory, in a heavily guarded convoy, to pray at the shrine considered by many Jews to be the burial place of the biblical patriarch. (MENAHEM KAHANA/AFP/Getty Images)

  • An Orthodox Jewish man blows the shofar horn along the beach in the coastal city of Ashdod, during the ritual of Tashlich on September 29, 2011. Jews traditionally walk to the nearest water source to hold the Tashlich prayer, in which they empty their pockets and throw the previous years "sins" into the water, ahead of Yom Kippur, or the Day of Atonement. (JACK GUEZ/AFP/Getty Images)

  • Jewish men blow the Shofar, a traditional instrument made of a ram horn, as fellow woman pray for relatives wishing to get married at the tomb of the ancient Jewish scholar Jonathan ben Uzziel in the region of Amooka, near the northern Israeli city of Safed on June 28, 2011. Thousands of practicing Jews, mainly unmarried women, visit the tomb to pray for finding a partner. (MENAHEM KAHANA/AFP/Getty Images)

  • A Jew blows a shofar, Ram's horn, while others pray as they perform Tasklikh, a Rosh Hashanah ritual for casting sins upon the waters, in front of the Mediterranean sea, in Ashdod, Israel, Thursday, Sept. 29, 2011. Tasklikh is when Jews symbolically throw their sins into moving water during the New Year holiday of Rosh Hashana. (AP Photo/Ariel Schalit)

  • Man blowing a <span class='searchmatch'>shofar</span>. Author: FotoFyl / Erifyli Tsavdari. Source: http://www. flickr. com/photos/fotofyl/43226645/ FotoFyl | http://www. <b>...</b>

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    Jewish man blows the shofar during the celebration of Sukkoth or feast of the Tabernacles at the Western Wall in the Old City of Jerusalem on Sept. 24, 2010. Thousands of Jews make the pilgrimage to Jerusalem during Sukkoth, which commemorates the 40 years of wandering in the desert after the exodus of Jews from Egypt some 3200 years ago. (JACK GUEZ/AFP/Getty Images)

  • A Jewish Indian boy blows the Shofar to gather devotees around the Torah at the Magen Abraham Synagogue in Ahmedabad on Sept. 9, 2010, on Jewish New Year Rosh Hashana. Synagogue President Benjamin Reuben numbered the Jewish community in Ahmedabad at 130, with an approximate total of 4,500 members in India whereof the majority, approximately 4,000, live in the financial capital Mumbai. (SAM PANTHAKY/AFP/Getty Images)

  • A newly arrived Jewish immigrant from the United States blows the Shofar upon their arrival at Ben Gurion International airport on Aug. 3, 2010. According to Nefesh B'Nefesh, the Israeli Immigration Authority, some 234 Jews from North America, including 85 new future Israeli Army soldiers arrived today in Israel. (JACK GUEZ/AFP/Getty Images)

  • A Jewish Indian boy blows the 'Shofar' horn to gather devotees around the Torah at the Magen Abraham Synagogue in Ahmedabad on Sept. 9, 2010, on Jewish New Year Rosh Hashana. Synagogue President Benjamin Reuben numbered the Jewish community in Ahmedabad at 130, with an approximate total of 4,500 members in India whereof the majority, approximately 4,000, live in the financial capital Mumbai. (SAM PANTHAKY/AFP/Getty Images)

  • Ultra Orthodox Jews blow the Shofar during a protest against the building company 'Electra', which according to protesters plans the removal of ancient Jewish tombs to construct a new building, in Jaffa just south of Tel Aviv, on July 28, 2010. (MARCO LONGARI/AFP/Getty Images)

  • An Israeli man blows a Shofar as others wait to welcome newly-arrived Jewish immigrant from North America at Ben Gurion International Airport near Tel Aviv on Sept. 8, 2009. According to the Israeli Immigration Authority, some 204 Jews arrived in Israel on this last plane, bringing the total of Jewish immigrants who arrived to Israel this summer to 3000. (JACK GUEZ/AFP/Getty Images)

  • Bulgarian Prime Minister Boyko Borissov (R) watches a Jewish rabbi blowing the Shofar, during his visit to the Western Wall, Judaism holiest site, in Jerusalem's old city on Jan. 12, 2010. (MENAHEM KAHANA/AFP/Getty Images)