Yom Kippur, the holiest day of the Jewish year

This year, Yom Kippur begins a few minutes before sunset on Tuesday, September 18th and concludes after nightfall on Wednesday, September 19th.

 PAINTING by the Polish artist Maurycy Gottlieb c. 1878, titled ‘Jews Praying in the Synagogue on Yom Kippur.’ (photo credit: Wikimedia Commons)
PAINTING by the Polish artist Maurycy Gottlieb c. 1878, titled ‘Jews Praying in the Synagogue on Yom Kippur.’
(photo credit: Wikimedia Commons)
Yom Kippur is the Jewish "Day of Atonement," the holiest day on the Jewish calendar. The day's laws and customs are intended to focus the individual completely on G-d. This year, Yom Kippur begins a few minutes before sunset on Tuesday, September 18th and concludes after nightfall on Wednesday, September 19th.
Jews traditionally mark Yom Kippur by refraining from eating or drinking for almost 26 hours and spending the day in synagogue, saying special prayers for forgiveness.
The day concludes the "Ten Days of Repentance" that begins with the Jewish New Year, Rosh Hashanah. During the entire Ten Days of Repentance special prayers called Selichot are said in the synagogue in the early morning or late at night, and other special additions are added to the customary daily prayers.
It is also customary in the period before Yom Kippur to ask forgiveness from friends and relatives. The atonement of Yom Kippur is not effective for offenses that a person committed against another person. One must ask for forgiveness and provide restitution if applicable (e.g. in the case of theft) to the person in question, and only then can a person seek forgiveness for God for the sin.
There is a custom on Erev Yom Kippur to perform a ritual called kapparot (literally, atonements). Money earmarked for charity or a chicken is waved over a person's head and special prayers are said. The ritual symbolically transfers a person's sins to the chicken, which is then slaughtered and donated to the poor. It is also customary to give tzedakah (charity) and for parents to bless their children with a special prayer before the fast begins.
It is considered a mitzvah to eat on Yom Kippur eve in order to have strength to complete the fast. A festive meal called the seudah mafseket (the final meal) is eaten about an hour before the fast. Some people have the custom of eating two festive meals, one in the morning and the final meal before the fast.
Many Jews have the custom to wear white to the synagogue to symbolize the purity they hope to attain by the end of the day.  Although Yom Kippur is a solemn day, it is also considered a holiday, since Jews should feel joyful and confident that God will forgive their sins which will enable a renewed spiritual connection with their Creator.