Simply put, it came from the Bible. Of course, the Bible doesn’t say explicitly anywhere, “The earth is 6,000 years old.” Good thing it doesn’t; otherwise it would be out of date the following year. But we wouldn’t expect an all-knowing God to make that kind of a mistake.
God gave us something better. In essence, He gave us a “birth certificate.” For example, using a personal birth certificate, a person can calculate how old he is at any point. It is similar with the earth. Genesis 1 says that the earth was created on the first day of creation . From there, we can begin to calculate the age of the earth.
The age of the earth can be estimated by taking the first five days of creation (from earth’s creation to Adam), then following the genealogies from Adam to Abraham in Genesis 5 and 11, then adding in the time from Abraham to today.
Adam was created on day 6, so there were five days before him. If we add up the dates from Adam to Abraham, we get about 2,000 years, using the Masoretic Hebrew text of Genesis 5 and 11. Whether Christian or secular, most scholars would agree that Abraham lived about 2,000 B.C. (4,000 years ago).
So a simple calculation is:
5 days
+ ~2,000 years
+ ~4,000 years
~6,000 years
At this point, the first five days are negligible. Quite a few people have done this calculation using the Masoretic text (which is what most English translations are based on) and with careful attention to the biblical details, they have arrived at the same time frame of about 6,000 years, or about 4000 B.C. Perhaps best, to check a recent work by Dr. Floyd Jones (Google it you will find him)
As I say I don't have all the answers but then neither does anyone, you make the assumptions that the figures given by evolutionists are correct, I have the assumption that what creationists say is correct, and no one has yet given me evidence to show that those assumptions are incorrect. It is about belief, my belief there was a creation
You believe differently not a problem to me.