A guest post by JS:
Writers are often told to "write what you know" so it is with that caveat that I admit I'm wandering into territory I'm not fully familiar with. I do so to spur conversation and bring up questions I have which I hope other people wonder about as well.
Today is the "minor fast day" of Shiva Asar B'Tammuz - The 17th of Tammuz. We fast because on this day the walls of Jerusalem were breached. It begins a 3 week period of mourning culminating in Tisha B'Av - The 9th of Av in which the Beit HaMikdash was destroyed.
However, the Mishna in Taanit (4:6) lists 5 reasons for fasting on this day:
1) Moshe broke the Ten Commandments;
2) The daily offering (Korban Tamid) ceased - there weren't enough animals during the seige of Jerusalem;
3) The walls of Jerusalem were breached;
4) An officer of Antiochus Epiphenes named Apostomos burned a Torah scroll; and
5) An idol was set up in the sanctuary.
What I find interesting is that we only focus on #3 (it seems the other 4 alone would not be important enough to warrant a fast day) as the minor fast days are collectively seen as a mini-chronology leading to the end of Jewish rule: Asara B'Tevet (siege of Jerusalem), Shiva Asar B'Tammuz (breach of the walls of Jerusalem), Tisha B'Av (destruction of the temple), and Tzom Gedaliah (end of Jewish rule).
Each of these fast days finds textual support in various books of Tanach. For example:
The siege of Jerusalem is recounted in 2 Kings 25:1-4 and Jeremiah 52:4 as occurring on the 10th day of the 10th month (10th of Tevet) and the assassination of Gedaliah is referenced in 2 Kings 25:25 and Jeremiah 41 as occurring in the 7th month (Tishrei).
However, the textual support for the 9th of Av of the 17th of Tammuz are less clear:
The destruction of the Temple is recounted in 2 Kings 25:8-9 as occurring on the 7th of 5th month (7th of Av) and in Jeremiah 52:12-13 as occurring on the 10th of the 5th month (10th of Av) . This is traditionally understood as meaning the inner sanctum of the Temple was entered on the 7th, the fire was started on the 9th, and it burned into the 10th. See Taanit 29a.
But, when were the walls breached? 2 Kings 25:3-4 and Jeremiah 52:6-7 indicate it took place on the 9th day of 4th month (9th of Tammuz). In fact, in Taanit 28b, the Babylonian Talmud expressly states that the 9th of Tammuz is when the walls of Jerusalem were breached during the First Temple period and the 17th of Tammuz is when the walls of Jerusalem were breached during the Second Temple period. So when all of the other events are so clearly related to the First Temple, why do we not fast on the 9th of Tammuz?
Interestingly, the Jerusalem Talmud in Taanit 4:4 states that our Tanach is wrong!!! The correct date is the 17th. It says there "קילקול חשבונות" - the prophet's thought process was disturbed and thus a mistake in the date was made.
Both the approach of the Babylonian Talmud and Jerusalem Talmud is odd. The former because all other fast days relate to the First Temple, the latter because they're arguing there's a significant distortion in two different places in Tanach.
More interesting is that the verses for the destruction of the temple are nearly identical except for the date, 7th versus 10th and yet no one (to the best of my knowledge) suggests "קילקול חשבונות" - the prophet's thought process was disturbed and thus a mistake in the date was made.
Search for more information about minor fast days at 4torah.com.