Here’s what is recorded in Exodus 6:2-3:
God spoke to Moses and said to him, ‘I am Yahweh. To Abraham, Isaac and Jacob I appeared as El Shaddai, but I did not make my name Yahweh known to them.
And yet in Genesis we have this (for example):
He then said to him, ‘I am Yahweh who brought you out of Ur of the Chaldaeans to give you this country as your possession.’ 8 ‘Lord Yahweh,’ Abram replied, ‘how can I know that I shall possess it?’ [Genesis 15:7-8]
(These quotations are taken from the JB, which more clearly demonstrates the problem than any other English translation I know of.)
In at least one of these places we cannot possibly be dealing with a literal historical record, because in Genesis 15 God is said to explicitly do exactly what He said in Exodus 6 that He didn’t do. Hence it simply cannot be the case that both Genesis and Exodus are intended to present literal history. Why? Because God cannot lie. But if both Genesis and Exodus are intended to present literal history, then God lied to Moses when He said that He did not make His Name known to Abraham. This is impossible. Therefore it cannot be the case that both Genesis and Exodus present literal history. It is possible that one of them may do so, or that neither of them does so, but not that both of them do so. Another alternative is that one or both consist of a mixture of literal history and other literature that is not intended to be literally historical.
Given these facts, it is at least possible that Genesis is not intended to be read as literal history. If that is the case, then there would be no reason based upon its literary type to suppose that Genesis 1 reports literal chronological historical data. This doesn’t necessarily rule out the possibility, but it does mean that we would have to be able to explain the conflict between Genesis 15 and Exodus 6. I can’t imagine any plausible way that the two can both be literally true, so one or the other necessarily must be non-literal in some way. Simply ignoring this problem and blithely taking Genesis 1 at face value won’t work. It doesn’t have to work, either. We’re obliged to hold that God created the heavens and the earth ex nihilo; we are not dogmatically bound to any particular view of the age of the earth.