Carbon-14 has a half life of 5730 years, meaning that 5730 years after an organism dies, half of its carbon-14 atoms have decayed to nitrogen atoms. Because of the short length of the carbon-14 half-life, carbon dating is only accurate for items that are thousands to tens of thousands of years old.

Is carbon-14 commonly used to date fossils or rocks older than 50000 years?

The carbon-14 method was developed by the American physicist Willard F. Libby about 1946. It has proved to be a versatile technique of dating fossils and archaeological specimens from 500 to 50,000 years old.