When Does Yom Kippur 2017 Start and End? Dates and Facts About the Jewish Holiday

Religious Jewish women pray at the women's section of the Western Wall in the Old City of Jerusalem on the eve of Yom Kippur also known as the Day of Atonement, the holiest day of the year in Judaism, on September 28. Thomas Coex/AFP/Getty Images

The most important holiday in the Jewish faith is Yom Kippur, which begins Friday evening. For those who are unfamiliar with it, perhaps beyond some inkling that it involves fasting, here are some basic questions asked and answered. Of course, every Jewish movement, community and family will have a slightly different way of marking this holiday, as is true of all others.

What is Yom Kippur?

Yom Kippur, the Day of Atonement, is the holiest day of the year and the most important holiday in Judaism. Yom literally translates as "day" in Hebrew and kippur comes from the same root as the verb "to atone" and the noun "atonement." The holiday is dedicated to introspection, prayer and forgiveness.

Yom Kippur is the culmination of the "Ten Days of Repentance" or the "Days of Awe." The period begins with Rosh Hashana, the Jewish new year, when according to the Jewish faith, God writes his judgment and the fate of each individual in the "Book of Life." The next several days are a time of self-reflection, prayer and repentance, providing observant Jews a chance to make amends and seek forgiveness for their sins and wrongdoings in the last year before their fate is sealed on Yom Kippur.

Rosh Hashana and Yom Kippur are also called the High Holidays or High Holy Days because of their utmost importance in the Jewish faith.

Related: What are the Jewish High Holidays? Dates and Facts About Rosh Hashana and Yom Kippur

When does Yom Kippur start and end in 2017?

In 2017, Yom Kippur starts at sundown on Friday, September 29, and ends at nightfall on Saturday, September 30. Technically, the date of the holiday is September 30 (the 10th of the month Tishrei on the Jewish calendar) but according to Jewish tradition, each day begins at sundown the night before.

Why is the exact date of Yom Kippur different every year?

Technically, it's not. Jewish holidays are determined by their dates on the Jewish calendar rather than the Gregorian calendar that the United States and most countries in the world use. Yom Kippur and all other Jewish holidays are celebrated on the same date each year on the Jewish calendar, which doesn't line up exactly with the Gregorian one. But they always come around the same time, with Yom Kippur generally marked in September or October.

As explained:

The Jewish calendar is lunisolar, or based on the cycles of the sun, around which the Earth orbits every 365 days, and the moon, which goes through a dozen waxing and waning cycles every roughly 354 days. Since a lunar month lasts about 29.53 days, each month on the Jewish calendar is either 29 or 30 days long. A regular year on the Jewish calendar, therefore, is about 11 days shorter than a full solar year. In order to fix the discrepancy and ensure that religious observances and seasons happen around the same time of year, it has its own version of a leap year. However, instead of adding one day to February, it adds a 13th month every two or three years (or precisely seven times every 19 years).

Why do many Jews fast on Yom Kippur?

The most well-known tradition associated with Yom Kippur is probably the fasting. But that is part of a much larger set of rituals. Yom Kippur is considered a day of rest, like Shabbat, which means that from the time the sun sets until the appearance of the first stars the following night, observant Jews do not write, shop, drive or ride in a car or another vehicle, perform any business transactions, cook or bake, turn on or off anything that requires electricity, and more. (That's why in Israel, many roads are entirely empty save for emergency vehicles and kids on their bikes on Yom Kippur.)

Yom Kippur is also a day on which observant Jews practice "self-denial" or during which they "afflict their souls." This means they do not eat or drink, apply lotions or creams, bathe or wash, wear leather shoes or have sex. According to tradition, all males 13 and older and all females 12 and older (starting at bar and bat mitzvah ages) must fast. However, the faith makes exceptions for those who are ill, need to take medications, are pregnant or have recently given birth. The idea is to consider spiritual rather than physical needs.

What other rituals are practiced before, during and after Yom Kippur?

Families will often gather for a meal before sundown in advance of the holiday called se'udah mafseket, or "concluding meal," and light candles at the end. They will also often reconvene the next day for a "break-the-fast" meal. Many Jews wear white on Yom Kippur, in some cases to symbolize purity and spiritual cleansing.

In addition to repentance and prayer, Yom Kippur focuses on charity. The kaparot is a symbolic atonement ceremony for which some observant Jews gather. A live chicken is passed over one's head three times, slaughtered according to traditional procedure, and then either the chicken or its monetary value is donated to charity. Not all Jews practice this particular ritual, which has angered animal rights activists, and there's now even an app that allows Jews to simulate the ritual sans chicken.

What kinds of prayers and services are conducted on Yom Kippur?

Yom Kippur is a prayer-heavy holiday. It begins in the evening with Kol Nidre, which translates as "all vows." It's a liturgical formulation chanted in Hebrew and Aramaic only on Yom Kippur to annul any unintended vows made to God over the last year, sometimes accompanied by the somber melody of a violin, viola or cello. According to tradition, it should be recited three times but some Reform congregations do so only once.

Yom Kippur services, which can last all day, contain several other prayers and readings, including Yizkor, a memorial prayer recited four times a year for those who have passed away. Neilah, which literally means "locking," is the concluding service at sunset. Afterwards, after night has fallen, the shofar, the horn of a ram or another animal, is sounded and it's time for the after-fast meal.