Rosh Hashanah 3 - What is special about the month of Nisan
Firstly, the New Year of the Jewish kings is counted from the same month as the Exodus. Why? Because of the phrase "In the four hundred and eightieth year from Exodus... in the fourth year of Solomon's reign, he built the Temple ." There is a comparison between Exodus and the years of a Jewish king, so they start counting from the same month.
But how do we know that the New Year of Exodus is indeed counted from Nisan? Granted that it is not Tishrei, because it is mentioned as not being the first, in connection to Moses' last speech. So too it is not Iyar, because Iyar is mentioned as second. Still, it could be Tammuz, Av, or Adar, which are not mentioned together with their count number. Rather, this is derived from an extra word in the story of King Solomon, who built the Temple in the second month, "in the second" - repeated. Why is it repeated? To tell us that Iyar is the second month, and therefore Nisan is the first.
In relation to this, the Talmud also discusses the chronology of king Koresh, and whether he was a righteous person. It is mentioned that a "shagel" was sitting to his right. This could alternatively mean a queen or a female dog. On the theory that he was righteous, the word is taken to mean a queen, but if not - it means his companion, a female dog.
Art: Moses By Antonio Zanchi