Geologic Time Scale Calculator
Look up geologic eon, era, period, and epoch for any age in years, Ma, or Ga.
Returns ICS classification and life forms from the Hadean to the Holocene.
Geologic Period
Geologic Time Units ka = thousand years ago | Ma = million years ago | Ga = billion years ago.
The Four Eons Hadean (4600–4000 Ma): Formation of Earth and Moon. No life. Archean (4000–2500 Ma): First life (prokaryotes). Earliest continents. Proterozoic (2500–541 Ma): Eukaryotes, multicellular life, first complex organisms. Phanerozoic (541–0 Ma): Visible life. Divided into Paleozoic, Mesozoic, and Cenozoic eras.
The ICS Chart The International Commission on Stratigraphy (ICS) maintains the official geologic time scale, updated periodically as dating methods improve.