Lunar geologic timescale
The lunar geologic timescale divides the history of Earth's Moon into six generally recognized geologic periods: Copernician[?] Period : -1100 MY to present Eratosthenian[?] Period : -3200 MY to -1100 MY Upper Imbrian[?] Epoch : -3800 MY to -3200 MY Lower Imbrian[?] Epoch : -3850 MY to -3800 MY Nectarian[?] Epoch : -3920 MY to -3850 MY Pre-Nectarian[?] Epoch: -4550 MY to -3920 MY