[ZULU]

You are right. There are minor problems with carbon 14 dating like changes in radioactive material in the atmosphere over time, or even bioplastic contaminants, but these can be corrected for.

When they are, its fairly accurate. Its generally given in + or - a certain number of years.

They also used thermoluminesce and potassium - argon dating
in addition to dendrochronology.

[B.Bumbleberry]

Potassium-argon I thought was only good to no later than about 200,000 years, after which the amount of potassium becomes unmeasureable. So it could hardly be used to calibrate carbon dates if that is true. That is why there has always been a struggle to date things between the latest dates of K/A and the earliest dates given by C. Thermoluminescence has been one technique to fill the gap, but I don't have a good understanding of that fairly recent technique. But it is an indirect dating technique, which would make it less desirable than carbon.

[Doctor Stochastic]

And all these methods give essentially the same results. Last month, "Science" had an article on calibration of carbon dating. One can use tree rings for ages of about 12,000 or so (this has probably been extended by now) and ice cores for longer ages. The first 12,000 tree rings, agree with the first 12,000 ice cores and with the carbon dating numbers. Note that the tree rings are taken from various continents as are the ice cores.

Of course, it could all be a Great Coincidence.