It would nice, of course, to reconcile the biblical account of Creation with the modern scientific one—and the idea that the biblical “day” there was not really a day as we know it, but something much longer, like, say, an eon, is the most common method for doing so.
The real problem with such an interpretation is the basic assumption that the authors of the Book of Genesis—or more to the point, the original conceivers of the Creation legend, which probably dates back to Mesopotamia, thousands of years before the Hebrew Bible was written—somehow had an authoritative knowledge of how the world was created. And there’s no reason to think that—unless, of course, you believe that they had a “direct line” to the Creator Himself. Which, of course, is the crux of the argument between believers and non-believers, and not an argument that we can hope to resolve here, or anywhere else.
But based purely on the Hebrew wording itself—no, there is nothing to suggest that a “day” in Gen. Chap 1 is anything other than a day as we know it. On the contrary, the story is intended to explain why days and nights came about, not just the world, and to demonstrate the magnificence of God for achieving all this within only seven days and nights.
(Originally written in reply to a question at Quora.com)