The age of 6000 years for creation comes from Usher, a theologian who took the given years in the Genesis genealogy accounts and added them all up. He came to 4004. That would be considered BC, adding 2000 years for AD.
Those who believe the earth is 6000 to 10,000 years old called Young Earth creationists. They hold to a minimum amount of years, a young Earth and creation, because of a very literal interpretation of the creation accounts and prehistory of Genesis 1-11.
However, when you look at other genealogies throughout the Bible, you will quickly find names not mentioned in the genealogies of Genesis 1-11. This presents a problem, because that means there are intentional gaps in the Genesis genealogies.
When Moses wrote Genesis, he was not concerned to give us every single link in the genealogy chain. He most likely had extra biblical sources to draw on for his genealogies. But they are meant to present a theological view of humanity.
For instance, Moses shows with Cain’s lineage that his descendents tended to be more wicked than the descendents of Seth. This is done on purpose, so we can see two separate lines, one more godly than the other.
The Bible wasn’t written to give us a blow-by-blow account of everything that happened in the history it covers. It was written that we might believe in God. It is a book of faith first. What it includes is accurate to history.
We don’t really know exactly how old the earth is. Scientists give us one impression while Scripture gives us another. It’s not that the two compete with one another. Because we don’t know exactly how many years passed between Genesis 1 and Genesis 11, and even after that, we cannot use Scripture alone to give us the age of creation.
The ancients weren’t overly concerned as we are today with the details. They were concerned with the message, see in the genealogies certain attributes and trends. They record the numbers with accuracy, but as I said, we don’t have the entire list.
We don’t have the numbers for the ones I in other genealogies. Based on the genealogies alone, we cannot come to an accurate assessment of the age of the universe. Science gives us a good understanding of the age of the earth.
But we must be careful not to look at bad science. Because no one was present at the beginning of creation, we cannot verify even with science the exact age of the universe. Some scientists hold two theories religiously. I say the right religiously or philosophically on purpose.
Scientists believe in these theories and hold to them as steadfastly as the most religious Bible thumper. They look to theories like evolution that are created for the sole purpose of keeping God out of the equation.
And religious people refuse to look at evolution as a possibility to explain the age of creation. The moment we know from hard data and reproducible experiments, we aren’t dealing with science anymore.
There’s nothing wrong with philosophy. There’s nothing wrong with theory. But if it can’t be proven in a lab, and no one can we create the universe in a lab, then we are stuck at an impasse if we hold to extreme views.
We must all agree that the Bible was not written to give us the exact age of the earth and universe just as much as science cannot give us the exact date either. We need to find a way to meet in the middle.