Another example to the one under discussion is the Babylonian calendar. Articles on the Jewish Calendar claim we got the leap month system from them. However, they went to the Metonic cycle of 19 years for computing leap months in 499 BCE. We were there already. Why is it more of a given that they had it first than the possibility that we gave it to the Babylonians?
Source of Hebrew Month Duration:Babylonian Science or Ancient Tradition?Morris EngelsonSummary.The best-known ancient value for the average length of the month is deduced (in sexagesimals) from Babylonian tablets of about 200 BCE. However, a statement in the Talmud, identified with the Hebrew Bible and allegedly older, says that the month is not less than a certain value, which, when converted to sexagesimals, is identical to the Babylonian one.This paper will:1. Demolish the argument that, because the modern month is less than this value, the Talmud is wrong.2. Show that it is not likely (though not impossible) that the Hebrew month duration was borrowed from the Babylonians.3. Conclude that the source of the Hebrew month is unresolved.http://www.dioi.org/vols/dio13v2-3.pdf