There actually is a serious theory that approximately 1000 years were added incorrectly. (In my opinion to distance us from the classical Roman civilization that was hated so much, but I digress.)

I read the first book of "History: fiction or science" by Anatoly Fomenko. He has a purely mathematical approach, proving that many historical writings from different epochs are really describing one and the same thing. And are thus of a similar age.

I personally couldn't point out any issues with his approach and believe he's right.

Can really recommend the book if interested.