List of time periods

The categorization of the past into discrete, quantified named blocks of time is called periodization. This is a list of such named time periods as defined in various fields of study. Major categorization systems include cosmological (time periods in the origin and mass evolution of the universe), geological (time periods in the origin and evolution of the Earth), anthropological and historical (time periods in the origin and evolution of human civilization).
Human time periods.
These can be divided broadly into prehistorical (before history began to be recorded) and historical periods (when written records began to be kept).
In archaeology and anthropology, prehistory is subdivided around the three-age system, this list includes the use of the three-age system as well as a number of various designation used in reference to sub-ages within the traditional three.
The dates for each age can vary by region. On the geologic time scale, the Holocene epoch starts at the end of the last glacial period of the current ice age (c. 10,000 BCE) and continues to the present. The beginning of the Mesolithic is usually considered to correspond to the beginning of the Holocene epoch.
Socio-cultural periods.
Only for late modern contemporary history.
Geologic time periods.
The geologic time scale covers the extent of the existence of Earth, from about 4600 million years ago to the present day. It is marked by Global Boundary Stratotype Sections and Points. Geologic time units are (in order of descending specificity) eons, eras, periods, epochs, and ages; and the corresponding chronostratigraphic units, which measure "rock-time", are eonothems, erathems, systems, series, and stages.
The second and third timelines are each subsection of their preceding timeline as indicated by asterisks. The Cenozoic is sometimes divided into the Quaternary and Tertiary periods, although the latter is no longer used officially.