There is a bit of a debate amongst believers regarding how to reconcile scripture with scientific claims about the age of the earth. Many assume that the evidence that the earth is millions of years old is water-tight, and therefore we only have three options: find a way to fit millions of years into the Bible somewhere, reject clear scientific evidence, or reject the Bible entirely. Those who do try to cram millions of years into scripture have to do it somewhere in Genesis 1. I've heard this done in two ways. One is the gap theory, which places millions of years in between Genesis 1:1, when God created the heavens and the earth, and Genesis 1:2, when the earth was without form and void. The idea is that earth was created once, destroyed, and then remade in between the verses. There's a fascinating book called "The Invisible War" by Donald Barnhouse that makes this claim fairly compellingly -- but so far as I can tell, even if one were to subscribe to this idea, the earth was still remade in Genesis 1:2--at which point the clock should start over. This won't "solve" the biblical young earth problem.

The other possibility uses 2 Peter 3:8, which says that "a day to the Lord is as a thousand years," to extrapolate that a day is also to the Lord as millions of years. Therefore, the six days of creation were actually millions of years apiece.
There are a number of philosophical problems with this. In certain places, scripture is poetic and should be interpreted as such. Psalm 91, for instance, says that "He shall cover you with His feathers, and under His wings you shall take refuge" (91:4).  This is obvious poetry, meant to evoke the image and feeling that God protects us the way a mother hen protects her chicks. It would be absurd to think this means that God has literal feathers. Many of the psalms employ similar poetic imagery, as do many of the prophetic books, Song of Songs, etc. These should be interpreted as poetry, and not as literal historical books.

But Genesis is written like an historical book. Genesis 1 is about as clear as it could possibly be that we're talking about six literal days. After each day the scripture says, "so the evening and the morning were the (blank) day," to illustrate that we are talking about 24 hours.

Also, Genesis says after each day, "And God saw that it was good." Death is not good; death is the result of sin (Romans 6:23). Sin didn't happen until Genesis 3. If each of the six days of creation was actually millions of years, do we suppose that no creatures died during that entire time? And if death did enter before Adam and Eve ever sinned, then how was creation pronounced "good"? Romans 8:19-22 tells us that even creation groans under the weight of corruption--it too must ultimately be redeemed. When did it become corrupted, if not by sin in Genesis 3?

Finally, if Genesis 1 is really a metaphorical abstraction representing millions of years of evolutionary change, what other apparently historical scriptures can be allegorized? Was there really a flood? How about a real resurrection?

In short, what can you trust? The Bible is either true or it's not.

If the Bible is literally trustworthy, what do we do with all the evidence that "proves" the earth is millions of years old? Does "science" actually prove this?

Carbon-14 dating is the best known dating method that most people think of in conjunction with this question. The most common isotope of carbon is C-12, but all carbon-based life forms start out with a certain, albeit very small, amount of the C-14 isotope in life. C-14 is radioactive, which means over time (after death) it decays via beta decay, in which one of its neutrons becomes a proton, turning it into nitrogen. The half life of C-14 decay is only 5700 years, give or take 30 years in either direction. That means it takes roughly 5700 years for half the amount of C-14 that started out in organic material to decay into nitrogen--so  you can't use C-14 dating for anything older than 100,000 years. Past that point, there shouldn't be any C-14 left.

And yet, some dinosaur bones have been found to still contain C-14 (https://www.icr.org/article/radiocarbon-dinosaur-other-fossils).  How is this possible, if they are supposed to be millions of years old?

Those who defend the evolutionary time scale will claim that the C-14 must have crept in via contamination.

Yet there are even more remarkable findings in dinosaur bones than C-14. Many still contain intact biomolecules (here's a comprehensive list: https://docs.google.com/spreadsheets/d/1eXtKzjWP2B1FMDVrsJ_992ITFK8H3LXfPFNM1ll-Yiw/edit#gid=0). These include hemoglobin and blood residue (https://www.icr.org/article/a-80-million-year-old-mosasaur-fossil), retinal tissue, and skin (https://www.icr.org/article/original-tissue-fossils-crea