Time is God's creation so whether He created mankind yesterday or 1,000,000 years ago makes no difference to me.
As my dad explained it to me like this when I asked him about God, us, dinosaurs and evolution – "1 day for God can be a billion years to us."
You see, time is God's creation, as I stated earlier. As such God is outside time and space. So "do not ignore this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day" (2 Peter 3:8).
The other thing is that the creation account in Genesis can believe in 1 of 2 ways:
- Happened as-is
- Happened somewhat like that
The key is that God created the universe, the sun, the moon, the earth, the animals, Adam, then Eve from Adam and we're all descended from our original parents. Outside of that Genesis was written at a time way before modern science and the audience was ignorant of such things so the Creation needed to be relayed in a manner that told hem exactly what happened but in a way they could understand.
There is only one Truth, whether it comes through scientific study or directly from divine revelation (Sacred Srcipture and/or Sacred Tradition) it will not contradict the other but rather reinforce both.