Today (Thursday, December 27), is the fast of the 10th of Tevet, one of the four days on which the Jewish people refrain from partaking of food in order to mourn the destruction of the Holy Temple.
The siege of Jerusalem began on this day, marking the beginning of the events that led to the destruction of the First Temple. The fast in Jerusalem began at 5:02 a.m. and it will conclude at 5:06 p.m.