Let me begin with this. I believe the creation poem that begins the Bible was a special revelation, traditionally given to Moses, that gives a true picture of the creation of the heavens and the earth as far as it goes in describing things. In it God painted with a very broad brush as he took us from the beginning of earth as an entity to the apex of his original creation—us.
I do not have a natural affinity for poetry so I have read books to help me better understand and appreciate it. One of the books made a very good point. That was that reading poetry literally was, in most cases, going to cause problems for the reader. You know where I am going with this: the problem of the days and nights.
First, I think that framing the creation account in terms of days and nights gives us a realistic feel for the way the heavens and earth were created in stages. Each of the stages is founded on a previous one and this is the way things occurred. All of physical creation, except at the very beginning, is dependent on something else that existed before it.
Second, I think setting the poem in a seven-day week enhanced the liturgical quality of the poem. This in turn kept it in the Tabernacle and Temple services so that it would come down to us as a suitable praise of God’s original works of creation.
We have, of course, many additional testimonies to God’s creation throughout Scripture, both of his original creation and of his continuing creation.