Precambrian super-era FACT FILE
The Precambrian is the largest span of time in Earth's history (seven eighths) before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale. It spans from the formation of Earth about 4.6 Gya to the beginning of the Cambrian Period, about 541.0 ± 1.0 Mya.
The 'Precambrian' is not used here, although it is often in use informally. Geochronologically the Archaean and Proterozoic are more useful.
*Based on 'The Geologic Time Scale 2012' by F M Gradstein, J G Ogg, M Schmitz & G Ogg (2012), with additions by the BGS.