Yom Kippur, also known as the Day of Atonement, is the holiest day in the Jewish calendar. It occurs on the 10th day of the month of Tishrei and is observed with fasting, prayer, and reflection. The day is dedicated to repentance and seeking forgiveness for sins committed over the past year. During Yom Kippur, many Jews attend synagogue services, where special prayers, including the Vidui (confession), are recited. The fast lasts from sunset to nightfall the following day, and it is a time for individuals to reflect on their actions and make amends with others and with God.