Radioactive dating is a means of finding the age of an organic compound. This is because there is always some amount of radioactive carbon present in the remains. These are evaluated and then compared with the standard half-life to find out the actual amount of carbon that must have been present and how old the remains must be.
Radioactive dative has been incredibly useful for dating back fossils and remains of mummies many centuries ack. It is considered very reliable and is an authentic means of evaluating the time since the creature died on the face of the planet using simple equations and mathematical formulas.