We are on earth though and the bible was dictated by God and given to us. Therefore we believe it is true. We can also apply logic and the book still stands. The book of Genesis also gives a yard stick to measure a "day", and a little logical progression makes it stand out. Read Gen 1:14. Therefore every day stands up to the same yard stick as the same verbage (for each day) was used in the account of creation. It may be that each day (and night) was longer (than we are used to), this we do not know (yet). It surely was different before Adam ate the apple with Eve.
Jeff