Two contrasting viewpoints on time divide prominent philosophers.
Usually this exercise is associated with a cross section or profile in which there are a series of stacked rock units composed of sedimentary, igneous, and/or metamorphic rocks as well as structures such as faults and folds (anticline, syncline) and unconformities (nonconformity, angular unconformity, If you have subsequent deposition of marine sediments (limestone, shale and sandstone) then the land mass must subside or the oceans rise to cover the surface by water before you can have deposition of sediments.
Some rocks and minerals can have their absolute age directly measured by analyzing the ratios of certain radioactive and non-radioactive isotopes they contain.
The units commonly used for geologic age are mega-annum (Ma) for millions of years, giga-annum (Ga) for billions of years, and kiloannum (ka) ka for thousands of years.
On the surface, radiometric dating methods appear to give powerful support to the statement that life has existed on the earth for hundreds of millions, even billions, of years.
We are told that these methods are accurate to a few percent, and that there are many different methods.