A: 1) Radiocarbon dating. Using a series of complex measurements and equations, we calculate the amount of Carbon-14 in a given fossil to determine its age.
2.) Floyd's Theory of Fossil Decomposition. Using a ten sided die, we choose a number from one to ten, throw a bunch of zeroes after it and call it a day. Named after Floyd, the security guard who invented the process the night he wanted us to leave early. Apparently he had Lakers tickets.
We use the first method if our boss is watching, or if we're dating the fossils of one of the more popular dinosaurs, like a Tyrannosaurus Rex. The second method comes in handy on Fridays or when someone discovers a pile of Apatosaurs.