Sivan is the third month of the Hebrew calendar. The name “Sivan” is of Babylonian origin, it is taken to mean “a time of harvest” and it appears only once in the Tanach, in the scroll of Esther 8:9.11:

 

So the king’s scribes were called at that time, in the third month, which is the month of Sivan, on the twenty-third day; and it was written, according to all that Mordecai commanded, … By these letters the king permitted the Jews who were in every city to gather together and protect their lives.

 

This was the happy end of the Purim story: Haman’s plan to annihilate the Jews had been overturned and the Jews’ right to defense was recognized.