EST 3:7

7 In the chodesh harishon [(first month)], that is, the month Nisan, in the twelfth year of HaMelech Achashverosh, they cast Pur, that is, the goral [(lot)], before Haman miyom l'yom [(from day to day, every day)], and me'chodesh l'chodesh [(from month to month, every month)] until the twelfth month, that is, the month Adar.