Interesting point of thought: Considering that a day is an earth-bound measure, how could you describe earth's creation in days if the concept of a 'day' did not yet exist?
Cause it's a story, meant to explain. You see, anybody with any real knowledge about the bible (AKA PHDs) hardly ever subscribe to any fundamentalist interpretation of any story. There are many stories which can be refuted by simple knowledge that they had BACK THEN, but the marvelous theing about this is, it doesn't mean that they aren't truth.