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