I recommend reading The Beginning of Wisdom: Reading Genesis, by Leon Kass. Kass is a Jewish professor of Old Testament. In his book, he treats Genesis as literature, and tries to understand it on its own terms. In dealing with the "seven days of creation," he doesn't get wrapped around the axle on whether it means seven calendar days of 24 hours each, but asks, what was the writer tryin to get across?
He points out that the Babylonians and all other cultures of the Middle East believed that the stars, planets, sun and moon were gods. The writer of Genesis is saying they aren't gods, they are created entities. The enumeration of created things starts with separating the land (fixed) from water (not fixed). Then come the celestial objects: things that move but are not alive. Then come the plants: things that are alive but don't move. Then come the animals, birds and fish: things that are both alive and move. You can't think of anything that doesn't fit in one of those categories.
The issue, according to Kass, is not time units as such, but seven (counting the day of rest) categories of created things, which are exhaustive and include everything in the universe.
In short, Kass is not treating Genesis literally, but recognizing that it is written in poetic language, and asking, what did the writer intend to convey to his readers?
Is he right? I don't know. However, it makes a lot more sense to me than trying to shoehorn the creation of the universe into seven calendar days, especially given what we know about the Big Bang and the age of the universe.
My year in a Catholic high school provided me with one unexpected perspective: The Religion Class (for that year, at least) combined religion with world history. That particular class had a logic all its own, and I have, since then, based my religious beliefs on logic.
Because of that one nine-month period in my teens, I have explored and discarded several religions as not being logical. The Universe is logical. Earth is logical. Therefore, God must be logical. If so, then it is my “job” to learn from Him, rather than tell Him what I want to believe.
Time, as the Bible states, was introduced for Man; Man did not invent Time. Because of that statement, and because of the logic of the Creation, I say that God, in His Wisdom, can tell us through His prophets that he created the Universe in six “days,” and that on the seventh, He rested. Those six “days” are not Monday through Saturday, as we perceive it. Those six “days” are God’s Days, and we are really silly to try and second-guess Him and pigeonhole His Creation into a format that we are able to explain.
I understand the need for theologians of any ilk to tidily tuck certain events of the Bible into little cubbyholes and try to explain away the things they don’t understand. If you have ever watched a “marathon” of religious programs in the six weeks before Christmas or Easter, you will understand what I’m saying. There are as many theories as there are theorists, but rather than debunk them, I watch, listen and glean. That’s my job, as I see it, on this earth.