While the stores are still pushing the holiday season, the holiday of Chanukah came to an end last Thursday. This upcoming Friday is another significant date in the Jewish calendar. This time the date marks a sad rather than a joyous occasion. Its date is 10/10, as Teves [sometimes spelled Tevet] is the 10th month counting from Nissan.
On the 10th of that month is day on which, 2438 years ago, Nebuchadnetzar, King of Babylon, laid siege on Jerusalem. That is what marked the beginning of the loss of the first Temple, which occurred nearly 3 years later on the 9th of Av. Like, the 9th of Av, the 17th of Tammuz, and Tzom Gedalia, this fast is, therefore, concerned with the loss of the Temple and Jewish sovereignty.
It shares the distinction of Yom Kippur of being observed as fast even if it falls out on the Sabbath. Practically speaking, it never falls out that way because of the calendar set up, but the theoretical possibility is significant.
In his blog, Rabbi Chaim Brown expounds on this point:
The same is not true even of 9 Av. Why is 10 Teves more significant than other fast days? Why should the beginning of the siege process that years later led to churban be more significant than the churban itself?
Chasam Sofer explains that 17 Tammuz is a fast which commemorates past events – the walls of Yerushalayim were breached. 9 Av is a fast which commemorates past events – the churban, among other tragedies, took place. Same for the fast of Gedlaya. Not so the fast of 10 Teves. True, the siege was put in place on 10 Teves, but other enemies has also laid siege to Yerushalayim and they were defeated. There was time yet to avert a churban. The fast of 10 Teves is not a fast that commemorates events which already occurred, but is rather a fast of an eis tzarah, a fast to avert future tragedy.
The failure to rebuild the Mikdash is tantamount to witnessing its destruction. The din v’cheshbon [spiritual reckoning] of whether this year will be another year of continued churban or whether this year will be the year we avert 9 Av and witness the rebuilding of the Mikdash occurs on 10 Teves. The future is in our hands to determine.
Two other events which are related to the first days of Tevet are the completionof the translation of the Torah into Greek on the Eighth of Tevet by the "Seventy Scholars" in the days of Ptolemy and the death of Ezra on the ninth of Tevet.
One more point about this date: The 10th of Teves is a day marked for remembering tragedies, even those that are not recorded. In the State of Israel, this is the day designated for saying Kaddish (the Jewish prayer for the deceased) for people whose date of deaths has not been determined. Read more at http://www.ou.org/chagim/roshchodesh/tevet/fast.htm