וּבַחֹ֙דֶשׁ֙ הַשֵּׁנִ֔י בְּשִׁבְעָ֧ה וְעֶשְׂרִ֛ים י֖וֹם לַחֹ֑דֶשׁ יָבְשָׁ֖ה הָאָֽרֶץ׃ (ס)
And in the second month, on the seven and twentieth day of the month, was the earth dry.
Tosefta Rosh Hashanah
How so, "for months"? Even though it says, "on the first month" and "on the second month"*i.e., in various verses in the Torah (see, e.g., Num. 20:1 ("in the first month"), Gen. 8:14 ("in the second month")), in which the ordinals "first" and "second" do not refer to a specific month of the year, but rather indicate the first or second month after a specific event (see Lieberman), they only begin to [formally] count from Nisan, as it says (Ex. 12:2), "This month shall be for you the first (lit., 'head') of the months."