Belive it or not there are records from the Greek and Roman Empires and other empires Like the Byzantine which account for most year. They were not illeterate fools.
Historians don’t just make things up guys. There is a written historical record that comes from secular sources, and there are times when there are multiple historical secular sources.
Of course they don’t make things up. But they do build huge mountains of extrapolation on top of small “facts”, such that if the small fact is not true, the rest is not either. And those small facts are frequently pretty unclear and inconsistent.
Hence why I called it hararim hatluyim b’saarah.
Or to paraphrase Mark Twain, they get such wholesome returns of conjecture with such a small investment of fact. (See Life on the Mississippi where he proves that the just over a trillion years ago next Tuesday, the Mississippi river used to jut out over the Gulf of Mexico like a fishing rod.)