The 10th of Tevet (known as Asarah B’Tevet) is observed as a day of fasting, mourning and repentance. They refrain from food and drink from daybreak to nightfall and add Selichot (penitential prayers) and other special supplements to our prayers. The fast ends at nightfall, or as soon as you see three medium-sized stars in the sky. (It is one of the minor fasts observed from before dawn to nightfall.)