The argument used is based on the fossil record and how long it took to develop those fossils, verse the unbiblical religious narrative that says the world is 6 to 7 thousand years old.
In Fact the age of the earth being 6 to 7000 years old is based on the genealogies found in the bible. Some guy way smarter than me went back and counted and made allowances for all the lives Recorded in the bible from Christ back to Adam, and then made an allowance from Adam's time till now. All we get is 6 to 7 thousand years.
Even so this is a provable fact, the bible never gives a time or age of the world and even though we have this genealogical record, The bible does not give us a mandate nor the right to age the earth artificially.
Because at best all we can do is determine how long the Fall of man/Adam's expulsion from the Garden was. I would guess that would be 6 or 7 thousand years ago.
However that does not tell us how long He and Eve were in the Garden before they were expelled does it?