One of My Favorite Jokes

For some reason, this is one of my favorite jokes. It's a very nerdy joke, but here goes:

Bob: "How old is the Universe?"
Dug: "20,000,000,019 years old."
Bob:"Twenty-billion and 19? How do you figure that?"
Dug: "I learned in astronomy class in college that the universe was twenty billion years old, and that was 19 years ago."

Here is a version of it I saw on the internet today that reminded me of it and I laughed: