Dinosaurs are fascinating creatures known only from fossils!  Some were massive, but others were the size of a chicken!  The average size was about the size of a sheep.  While the fossil record reveals many things about these fascinating creatures, can we be certain that they lived "millions of years ago"?  Since dinosaur fossils don't come with tags on them that say: "65 million years old," how do we know scientifically that they are that old?  In short, "millions (or billions) of years" is not science since it cannot be observed, tested, or repeated.