A geological period is one of several subdivisions of
The twelve currently recognised periods of the present eon – the
A consequence of this approach to the Phanerozoic periods is that the ages of their beginnings and ends can change from time to time as the absolute age of the chosen rock sequences, which define them, is more precisely determined.
The set of rocks (
The following table includes all currently recognized periods. The table omits the time before 2500 million years ago, which is not divided into periods.