<Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (December 2016) (Learn how and when to remove this template message) </Td> </Tr> <Table> <Tr> <Td> </Td> <Td> This article or section possibly contains previously unpublished synthesis of published material that conveys ideas not attributable to the original sources . Relevant discussion may be found on the talk page . (May 2017) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article or section possibly contains previously unpublished synthesis of published material that conveys ideas not attributable to the original sources . Relevant discussion may be found on the talk page . (May 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> 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 (time periods in the origin and evolution of humans) and historical (written history). </P>

What are the different ages of the earth