Re: “It’s clear that there was no universe before day one.”
Not necessarily. The Bible says, “In the beginning God created the heavens and the earth, and the earth was without form and void.”
The universe and the earth could have been around any number of years prior to the events of verse two where it says that the “Spirit of God was hovering over the face of the waters” and Him beginning His creative acts upon the earth and the universe described later in the chapter.
But day 4 is when the rest of the universe other than the earth is created.