Sunday is the 10th of the Jewish month of Tevet, one of four days of fasting set by Jewish sages related to the destruction of the Temple in Jerusalem. The date marks the start of the siege that led up to the destruction of the First Temple by the Babylonians. Since the start of the modern state of Israel, it is also the day of a general Kaddish for those who were murdered in the Holocaust, with a specific focus on those whose date of death is not known. The fast runs from dawn (5:05 a.m. in Jerusalem) to nighfall (5:03 p.m.)
There are those who take on individual fasts on the 8th of Tevet to mark the translation of the Torah to Greek known as the Septuagint. Despite miracles associated with the translation, reading it in anything but Hebrew leaves room for misinterpretation. There are also those who fast on the 9th of Tevet, the anniversary of the deaths of Ezra and Nechemiah, who re-established the Temple after the Babylonian captivity.