Purim is a festival that commemorates the deliverance of the Jewish people of the ancient Persian Empire from Haman's plot to annihilate them, as recorded in the biblical Book of Esther (Megillat Esther). According to the story, Haman cast lots to determine the day upon which to exterminate the Jews. Purim is celebrated annually according to the Hebrew calendar on the 14th day of the Hebrew month of Adar (Adar II in leap years), the day following the victory of the Jews over their enemies.