Yom Kippur, the Day of Atonement, is on the 10th day of the Hebrew month of Tishrei. It is the second of the two "High Holy Days," following Rosh Hashanah at the beginning of that month.
It is the only major Jewish observance where those over the age of 13 are required to fast for an entire day. As with all Jewish holidays and observances, it begins in the evening and ends 25 hours later. The day is traditionally spent mostly in prayer, with sessions of Bible study and discussions. Pledges are made to each other, and to God, about being one’s best self.
1. Jews abstain from more than food.
The fast is not only from food and drink, but also from sexual relations, wearing leather, or using perfumes. In Biblical times, these last two items were marks of wealthier people, and so today humble dress, as well as humble attitudes, are part of the observance.
2. The full name is Yom Hakippurim, the Day of Atonements.
Technically, the name is plural. All the confessions are done as a community, and chanted in the first person plural: "We have sinned." This public ritual is said to create a supportive and bonding experience.
3. Forgiveness is a big theme.
In the days leading up to Yom Kippur, people have asked for forgiveness from all their loved ones. One cannot ask for God’s forgiveness, the main point of the day’s activities, until one has been forgiven by the humans involved.
4. There are some creative lists of sins.
There are several lists of sins, all in Hebrew alphabetical order, forming acrostics. In modernity, some very clever writers have translated them into English and largely kept the alphabetical order; for example, a recitation would go along the lines of "We have abused, betrayed, been cruel, destroyed, embittered others," etc. Almost all of these sins are about the ways people treat each other, not how they treat God: violence, rushing to judgment, lack of compassion, indifference to evil, etc.
5. In ancient times, it wasn't a great day for goats.
In the Biblical era, two goats were chosen by lotteries. One was ritually sacrificed to atone for the sins of the people, and the other, as an act of purification, was driven off into the wilderness, and some say over a cliff. This was, of course, the "scape-goat."
6. There are some less-expected reasons for fasting.
In addition to fasting as a display of true repentance and to create a less worldly focus, the experience of truly being hungry is supposed to arouse maximum compassion for the poor. It is traditional to make a charitable donation of at least the amount one would have spent for one’s family that day.
7. It is the only holiday where the evening service starts before sundown.
This evening service has a special name: Kol Nidrei, which is also the name of the most important Yom Kippur evening prayer. In it, God is asked to annul and forgive all oaths made under pressure. This is a reference to the religious oaths made in eras when Jews were forced to convert, usually to Christianity, or die.
8. There's also a memorial candle-lighting.
Since the Holocaust, Jews light a memorial candle for the six million who perished, as well as for departed relatives.
9. Even the Torah gets a special outfit.
It is customary to wear all white as a symbol of purity and of a new start. Even the Torah scrolls have special white mantles (coverings) for the High Holy Days. Traditionally, men (and in modern times, women) wear a plain white robe over their clothing, called a kittel. This is worn again for the Passover seder, and is the garment in which they are later buried.
10. Dancing used to be involved.
It is said that in the Biblical era, during the late afternoon of Yom Kippur, the unmarried maidens would dance in the forest clearings, and the unmarried young men would watch, hoping to know which was meant to be his bride.