A guy one day goes to a museum that has a dinosaur exhibit.

He spends a few hours wandering around and admiring the skeletons of a variety of dinosaur species. At one point he stops in front of a particular exhibit trying to get some sense of its actual size and age of this magnificent creature. He notices not too far from him a museum worker and says to him, “Quite a beast. I wonder how old it is.”

The museum worker points to the dinosaur skeleton and says, “This one? This one is 70 million years old and six months.”

“Wow,” the guy says. “That is pretty specific. How can they be that accurate?”

“Well,” the museum worker replies. “This one was 70 million years old when I started working here, and that was six months ago.”