However, even with such historical calibration, archaeologists do not regard C produced and therefore dating the system.
Overall, the energy of the Earth's magnetic field has been decreasing, so more C is being produced now than in the past.
This will make old things look older than they really are.
These techniques, unlike carbon dating, mostly use the relative concentrations of parent and daughter products in radioactive decay chains.
For example, potassium-40 decays to argon-40; uranium-238 decays to lead-206 via other elements like radium; uranium-235 decays to lead-207; rubidium-87 decays to strontium-87; etc.
These techniques are applied to igneous rocks, and are normally seen as giving the time since solidification.