It's clear that there was no universe before day one.
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.
Actually it’s clear that there was at least part of a day 0 before day one. Day one is, as is the Hebrew sense of days, from a sunset to a sunset, an evening and then a morning, a night and a day.
His announcing the dawn, “Let light be”, didn’t happen during the night and day reckoned to be day one, but instead on this “day 0”, IOW the separation of night from day happened after He said “Let light be” just as the text presents it.
Creation of physical existence happened before He said “Let light be”.
A first reckoned day can be nothing more than the first day of a new epoch, an official calendar. Have you not read that there has been more than one such epoch recorded in the Bible: the times before the flood and the times after it in particular, wherein both Earth and the heavens have been changed?
The earth was already present before the first reckoned day. YEC is unnecessary to a literal reading of Genesis and is a superfluity.