A time period as small as a million of years is already impossible for me to grasp. That's a dozen time longer than the human history, and my awareness of it goes back to 4-6 thousand at most. I know the important milestones that happened before that, but I cannot picture them on a time scale – it all fades into a couple of dudes sitting in a cave for what seems like an eternity, amidst which all major migrations happened in a blink of an eye. Multicellular life doesn't have a billion years yet. If someone bumped in me on the street and asked me was the universe billions of years old, and I didn't have an interest in the matter, I would not know how to answer as billions and millions would sound the same to me.