yeah 6000 years my bad.
The bible lists the geneologies of Christ in several places. Starting with Adam, the age of the majority of those listed in the bible is given, for example abraham, jacob, joseph, and david, their age at their death is given. Its not difficult to estimate to within a few hundred years the age of the earth based on bible geneology.
When you consider carbon dating......there's a difference of a few billion years.
You also have to assume that:
1. The genealogies are literal, and that no generations were skipped.
the word
yalad that is translated as begat in the OT can mean the father of, but it can also mean the ancestor of.
2. That people really did live to be 800-900 years old, and that a year as described in the bible is the same 365 day period that we call a year today. The word
sana that is translated as years in the OT can also mean year, years, two years, year by year, yearly, and an entire age.
3. That the creation days were literally six 24 hour days.
Yom, translated as day can mean a literal day or it can also refer to a period of time, which I think is the case in the Genesis creation narrative. You also have to consider that a 24 hour day as we know it is impossible without the sun, which wasn't even created until the fourth day. Also, the bible dosen't say that God created the earth on the first day, He created light on the first day. He created the earth
in the beginning, which could have been at any point in the past. You should also consider 2 Peter 3:8, which says that a day is as a thousand years and a thousand years as a day with God. To me that simply means that the concept of time is meaningless when we are talking about God.
It is impossible to take the bible and pinpoint a date for the creation of the earth, nor do I think it was ever intended to do so.