We know that this took place on a Monday, because it was two days before Bellarion's impeachment by the captains, which in turn was four days before a Sunday [Chapter 3.XII].  This Monday could not have been November 7, the first day of the siege, because three assaults on the city had already been repulsed.  But if it was Monday the twenty-first or the twenty-eighth then Theodore's final defeat was in December, and we know that it was a "November night" when Bellarion's army returned triumphant [Chapter 3.XIV].  Thus November 14 is the only possible day.