4.6 to 3.8 billion years ago
The Hadean includes the first 800 million years of Earth's history - the time of the formation of the planet from a presumably molten mass. The oldest dated rocks found so far are from Canada and are dated at 3.96 billion years old, the end of the Hadean. Any older rocks either are deeply buried and yet to be found or have been remelted and recycled. Meteorites and moon rocks date from this ancient time when the Earth's crust was forming and was continually bombarded by meteorites and comets.