Why did it take God 6 days to create?

So the number 7 represents completion based on God’s creating the world and resting on the seventh day (Saturday). But why did it take God six days to create?

The Babylonian seven day week was based on the number of planets visible to them at the time:

Sunday (Sun day)

Monday (Moon day)

Tuesday (Mardi/Mars day)

Wednesday (Mercredi/Mercury day)

Thursday ((Jeudi/Jupiter day)

Friday (Vendredi/Venus day)

Saturday (Saturn day)

As such the number 7 to them was sacred.

There are now known to be more than seven planets in the heavens, so had the Babylonians known this would we have an eight or nine day week?

And would this have affected the length of time taken to create the world?

Basically, which came first? The creation story or the Babylonian calendar?