Absolute time is the measurement taken from the same rocks to determine the amount of time that has expired. Absolute time measurements can therefore be used to calibrate the relative time scale, producing an integrated geologic or "geochronologic" time scale that combines both types of data, as is depicted here.
This geologic time scale is based upon data from Harland et al.
Absolute dating is the process of determining an age on a specified chronology in archaeology Other radiometric dating techniques are available for earlier periods. One of the most widely used is potassium–argon dating (K–Ar dating).