The Gemmorah in Jerusalem Rosh Hashana 6a explains the process of adopting the Babylonian names instead of Biblical ones.
דא"ר חנינה שמות חדשים עלו בידם מבבל
R'Hanina said: the names of the Months were brought with them from Babylon
WIKI on Metonic_cycle claims that the 19 years 12/13 month cycle was used by Babylonians [at least] from the times of the First Temple:
"According to Livy, the king of Rome Numa Pompilius (753-673 BC, [mid first Temple]) inserted intercalary months in such a way that in the twentieth year the days should fall in with the same position of the sun from which they had started."
I'm looking for counterexamples in our sources, that the Jewish calendar as we know it was practiced prior to the Babylonian exile.
Are there verses that Bney Israel kept Kiddush HaChodesh and Ibbur Hashana from Yehoshua till the destruction of the First Temple?