When the Lord says that “the evening and morning were the first day,” I believe Him. He’s MORE than able to do it in six, literal “24-hour” days.
Of course whatever the Bible says is true. But it’s not always literal. For instance, when Paul says in Ephesians that Jesus is the Cornerstone of the Church, he certainly means it—but not with complete literalness (e.g., that Jesus is literally a stone).