Original: The Proterozoic Eon extended from 2500 Ma to 542.0 Â 1.0 Ma (million years ago), and is the most recent part of the old, informally named â Precambrianâ time.
Simplified: The Proterozoic Eon extended from 2500 million years ago to 542mya, and is the most recent part of the former Precambrian.