“Except the Bible clearly tells us each day was “evening and morning”, so they are obviously terrestrial days marked the same way that we mark them.”
Except the sun wasn’t made until day four... Where did the evening and morning come from?
Genesis 1:3 First day.
The Almighty did quite a lot in that first day.
“Where did the evening and morning come from?”
From God. When God says it is evening, it’s evening. Just like when God says “let there be light”, there is light.