I was reading many articles about estimates of the age of the Earth throughout the ages. I was dumbfounded when I read that Newton, arguably one of the greatest scientists ever to have ‘calculated’ the age of the earth, estimated that the Earth was created in 4000 BCE. Johannes Kepler arrived at a similar result. Which methods did these scientists use to arrive at such conclusions?
The estimates of Newton and Kepler, and the similar estimates of dozens of their contemporaries, were produced by treating the Bible as a historically accurate document and deriving a chronology from it. I think that a detailed explanation of their techniques would be off-topic for Earth Science, but the Wikipedia page on the Ussher Chronology (which provides probably the most famous biblically-based estimate of the Earth's age) goes into reasonable detail about the methods used for such calculations.