The Hadean is, according to atheist scientists and Old Earth Creationists, the geologic eon that started at their estimated date for the Creation or formation of the Earth, 4.6 billion years ago, and ended approximately 3.8 billion years ago. Young Earth Creationists reject these estimates, and maintain that the Earth was created approximately 6000 years ago.
This name owes its name to Hades, the Ancient Greek underworld, reflecting the scientists' estimates on what the conditions on Earth would have been at the time.