Genesis is actually silent on that, saying nothing about the age of the universe or earth before Genesis 1:1.
It's clear that there was no universe before day one.
I thought it took a week for God to put it all together. Then the Jews wrote the history itemizing the birth from Adam on and his descendants along with their multi-centuries long lives. I saw a lot of detail there in Genesis. Most Biblical Scholars put the age of the Earth about six thousand years old. Just add the week of God's work to get the age of the universe. Not so silent to me. Of course, it is not congruent with geology, genetics, archeology, paleontology, and cosmology.
It does have a pretty good timeline beginning from the fall.