How is the age of the earth used as evidence of evolution?

The age of the earth can be used as evidence of evolution because it withholds the past that we are capable of uncovering bit by bit. We excavate fossils buried in the ground which we use accordingly. The fossil record reveals that the deeper you go, the farther back in history you unearth. This is known as the Law of Superposition. With these fossils, we can compare and contrast the anatomy of closely related organisms and possibly uncover vestigial structures. All of which is evidence that evolution has taken place.