The first month of the biblical festival year — the later name for the month of Aviv
In Scripture World English Bible
In the first month, which 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, and chose the twelfth month, which is the month Adar.
In the month Nisan, in the twentieth year of Artaxerxes the king, when wine was before him, I took up the wine, and gave it to the king. Now I had not been sad before in his presence.