Standard Global Chronostratigraphic (Geochronologic) Scale
This scale is a hierarchical system of stratigraphic units around the world and is composed of eonothems, erathems, systems and series (and the corresponding chronostratigraphic units, such as eons, eras, periods and epochs, respectively). It serves to provide a standard for identifying all rock ages and linking all rocks around the world with the global geologic history. The units listed in the Standard Global Chronostratigraphic Scale are equivalent to the corresponding time spans, and it is theoretically globally applicable. This scale is also called the geologic time scale.