13 Tishrei

c 1877 BCE- After Avraham was unable to find ten righteous people in whose merit S'dom could be saved, G-d totally destroyed S'dom, Amora, Admah, and Tzvoyim.  Tzoar, a "younger" city with less of a history of evil, was saved, after Lot and his daughters insisted on taking refuge there. (Genesis 19)