3:7 In the first month, that is, the month Nisan, in the twelfth year of king Ahasuerus, they cast Pur, that is, the lot, before Haman from day to day, and from month to month, to the twelfth month, that is, the month Adar.
first month i.e. April; Esther 3:12
twelfth month i.e. March; Esther 3:13