Lunar geological time scale

The lunar geological time scale is a division of the past history of the Moon in geological time:
Copernican Period: from 1100 billion years ago  to the present.
Eratosthenes Period: from 3200 to 1100 billion years ago.
Period Imbriano higher: from 3800 to 3200 billion years ago.
Period Imbriano below: from 3850 to 3800 billion years ago.
Nectarian Period: from 3920 to 3850 billion years ago.
Pre-Nectarian Period: from 4550 to 3920 billion years ago.