Direct radiometric dating accuracy
One problem with argon-argon dating has been a slight discrepancy with other methods of dating.) reports that a correction of 0.65% is needed.Thus the Cretaceous–Paleogene extinction (when the dinosaurs died out) - previously dated at 65.0 or 65.5 million years ago - is more accurately dated to 66.0 Ma. It is an accurate way to date specific geologic events.There are many radiometric clocks and when applied to appropriate materials, the dating can be very accurate.
Ar after cooling past the closing temperature and that this was properly sampled during analysis.
Similarly, the Permian-Triassic extinction is now dated at 252.5 Ma, which is effectively coincident with the age determined by other means for Siberian Traps basalt flows.
This is an enormous branch of geochemistry called Geochronology.
We know it is accurate because radiometric dating is based on the radioactive decay of unstable isotopes.
For example, the element Uranium exists as one of several isotopes, some of which are unstable.