Esther 3:13 Letters were sent by couriers to all the king's provinces to destroy, to kill and to annihilate all the Jews, both young and old, women and children, in one day, the thirteenth day of the twelfth month, which is the month Adar, and to seize their possessions as plunder.

Esther 9:1 Now in the twelfth month (that is, the month Adar), on the thirteenth day when the king's command and edict were about to be executed, on the day when the enemies of the Jews hoped to gain the mastery over them, it was turned to the contrary so that the Jews themselves gained the mastery over those who hated them. (NASB ©1995)