Geochronology is the
science of determining the absolute age of
rocks,
fossils, and
sediments, within a certain degree of uncertainty inherent within the method used. A variety of dating methods are used by geologists to achieve this.Geochronology is different in application from
biostratigraphy, which is the science of assigning sedimentary rocks to a known geological period via describing, cataloguing and comparing fossil floral and faunal assemblages. Biostratigraphy does not directly provide an absolute age determination of a rock, merely places it within an interval of time at which that fossil assemblage is known to have coexisted.
See more at Wikipedia.org...
The study of the relationship between the history of the Earth and time.