Halakhah su Ester 3:7

When the new moon comes again at the time of ripening in the Land of Israel, then one year is complete, whether the year is twelve months or thirteen. For this reason, in Hebrew they did not refer to the month of ripening as Nisan, rather “first.”⁸⁰ The first month in the Hebrew calendar might not always coincide with the Babylonian month of Nisan. The same is true for all the months. Therefore, other than in books of the exilic period, you will not find in the twenty-four books (the Hebrew Bible)⁸¹ The canon for the Hebrew Bible contains 24 books: Pentateuch (5), Early Prophets (4), Later Prophets (4), Psalms, Proverbs, Job, Daniel, Ezra-Nehemia, Megilot (5), and Chronicles. names for the months as they are known today, of which the first is Nisan.⁸² The names used for the months of the Hebrew calendar – Nisan, Iyar, etc. – for approximately the last two and a half millennia are Babylonian in origin. These names were adopted by the Jews after the destruction of the first Temple. Until that time the months were not given names and were referred to numerically – first month, second month, etc. So the year for Israel does not begin with the equinox, rather with the day of the new moon. Once we know that this month is the first, we observe the holidays in the seventh month from it. Thus, if Passover was in the days when the barley ripens, then Pentacost will be at the time of cutting and Tabernacles at the time of gathering.

Know that the Chaldeans do not have a second Adar, because their months are not lunar months.¹⁰⁸ See Evans (p. 187) where he describes the Babylonian calendar as also a lunisolar calendar with a second Adar. Also see Otto Neugebauer, The Exact Sciences in Antiquity, p. 102. Instead they divide the solar year into twelve parts. The meaning of the verse “In the first month, the month of Nisan” (Esther 3:7), is that in that specific year it was so, for in an intercalated year the first month would have been Iyar. Therefore, it is not correct to translate “in the first” (Joel 2:23) as “ in Nisan.” ¹⁰⁹ This is how the term is rendered in the Aramaic translation of Jonathan ben Uziel. This was done so that people at that time would understand.