C14 dates can be fairly accurate within about 4500 years. Beyond that it has always been known C14 testing is useless. You can get back to about 4500 years ago if calibrated correctly. Quoting: Anonymous Coward 76693275
45,000 to 50,000
That's what we were taught, but the reality is different.
The reality is that the spreads we get on th dates we get for anything older than about 6,000 years BP are so wide that they are useless.
For example, we tested charcoal from a firepit at a Clovis site dating to about 12,000 years ago.
6 test were performed on charcoal from different areas of the pit.
The date range was from 9,000 to 40,000 years BP! With a midpoint of about 25,000 BP, and the Clovis culture thought to have appeared about 13,000 years ago, only the lowest date is considered usable, but goes against standard practice, which is to take the average. Because of this we had to disregard the whole sequence.
We were disappointed, to say the least!