Not necessarily so. While I believe the "Six Days" was a literal measure of time, the question is from whose perspective was it measured?
Genesis Ch.2 V.4 "These are the generations of the heavens and of the earth when they were created, in the day that the LORD God made the earth and the heavens,"
Genesis Ch.2 V.17 "But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die."
Clearly the use of "DAY" does not refer to a 24 hour span of time - from our perspective, nor does it mean that in any of the other instances where "in the day that" is used.
Ecclesiastes Ch.3 V.15 "That which hath been is now; and that which is to be hath already been; and God requireth that which is past."
Time doesn't appear to be "linear" in its form as viewed by the Sovereign. It, too, is the created, subject to the Creator. If Moses transcribed God's words as He spoke them, the translation of DAY from God's POV to Moses' POV, and subsequently ours, would definitely have had different meanings. (In the first few "DAYS" of creation, there wouldn't have been the capacity to measure a "day" as 24 hours relative to the sun and earth.)
However, God gave His word of truth to the patriarch Moses and "Six Days" are the spoken word. Since the prince of this world is Satan, the Deciever and father of lies, it's possible for Satan to use every ploy to decieve those who would trust their own sight rather than believe God's word. None living has seen God, yet we believe He is. We see an "Aged Earth", but it could be we see a Universe that "appears" as what it is not - like a hologram appears to have more dimension than there actually is.
The final question is do we live by faith or by sight. If we live by sight, then belief in God's being is questionable. If we live by faith in God's spoken word, then God's word should have more influence over our perception of the world. Whether "DAY" is 24 hours or 24 million years becomes irrelevant. It's the same mincing of words Satan did with Eve in telling her "surely you will not die" when he knew she wouldn't die immediately....
Clearly the use of "DAY" does not refer to a 24 hour span of time - from our perspective, nor does it mean that in any of the other instances where "in the day that" is used.
He meant spiritual death, which did in fact occur that very day.