Most theologians today consider the first chapter of Genesis to be a response to the Babylonian creation epic called the Enuma Elish. Both accounts are concerned with the conquest of order over chaos. The Enuma Elish begins with “When on high,” and Genesis begins similarly, although with a unique Hebrew spin, with “In the beginning.” Also, the view of creation in Genesis seems derivative from the description in the Enuma Elish, although with a clearly transcendent view of God. But since there are many other interpretations, and nobody really knows which one might be correct, if any of them, I wanted to discuss my favorite.
The earliest civilizations, including the Babylonians, were thought to have been star gazers. There are five planets that can be seen without a telescope: Mercury, Venus, Mars, Jupiter, and Saturn. Planets move differently through the night sky than stars. They disappear and reappear, moving as they wish, or so it might seem if you didn’t know they were planets. To the ancient mind they were gods.
That makes for seven heavenly bodies worshipped by ancient cultures: the sun, the moon, and the five visible planets. They celebrated the seven day week around their worship of these seven heavenly bodies. For example, the sun god was concerned with bringing light into the world every morning. Our English language still carries this remembrance. Sunday is a day in honor of the sun; Monday is a day to worship the moon; on up to Saturday, which is the day for Saturn. The days of the week are capitalized because they were once considered gods. his weekly worship was somehow transferred to the Germanic languages and found its way to our English.
The writer of Genesis had no intention of honoring these gods. There was one God and one Creator of the world. Instead of the sun god being responsible for bringing light to the world, YHWH created light on the first day. The names of the week are not even mentioned in the first chapter because they were the names of gods. The days certainly had their names before Genesis was written, but they are purposely left out. Instead, they are simply called the first day, the second day, the third day, etc. In other words, the first chapter of Genesis was written around a seven-day week in opposition to the religious worship of Israel’s neighbors, not because of an actual description of creation.
Now you may accept this explanation or not. Nobody knows how Genesis is written, and many have other favored interpretations. I wrote this to illustrate that there are other options to a literal seven-day reading of the first chapter. There is no need to read the Bible in that manner in order to take its message seriously.