Absolute dating and relative dating are both used commonly to determine the age of fossils. Absolute dating gives the exact date and chronological order to which the fossil lived. They do this by looking at the surrounding ground and using the carbon to find out how old it is. Relative dating is pretty similar to this except it uses carbon dating which is a way of finding the approximate age of the fossil. They do this by looking at the layers of the earth and making an assumption as to how old it is.
