Radiometric dating of detrital minerals in sedimentary rocks gives
In geochronology, time is generally measured in mya (megayears or million years ago), each unit representing the period of approximately 1,000,000 years in the past.The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet.Each eon saw the most significant changes in Earth's composition, climate and life.Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs. The moon is formed around this time, probably due to a protoplanet's collision into Earth.The Archean and Proterozoic eons follow; they produced the abiogenesis of life on Earth and then the evolution of early life.The succeeding eon is the Phanerozoic, which is represented by its three component eras: the Palaeozoic; the Mesozoic, which spanned the rise, reign, and climactic extinction of the non-avian dinosaurs; and the Cenozoic, which presented the subsequent development of dominant mammals on Earth.
The age of the Earth is approximately one-third of the age of the universe.
Hominins, the earliest direct ancestors of the human clade, rose sometime during the latter part of the Miocene epoch; the precise time marking the first hominins is broadly debated over a current range of 13 to 4 million years ago.
The succeeding Quaternary period is the time of recognizable humans, i.e., the genus Homo, but that period's two million-year-plus term of the recent times is too small to be visible at the scale of the GTS graphic.
(Notes re the graphic: Ga means "billion years"; Ma, "million years".) The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago, during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon.
There are microbial mat fossils such as stromatolites found in 3.48 billion-year-old sandstone discovered in Western Australia.