Related Clues:

• Many, many millennia
• Astronomical time period
• Lot of time
• Division of about one billion years
• Long long time
• Moment in time, in astronomy
• A unit of geological time
• Billion-year period
• A bazillion jillion years
• Indefinable time period
• Era upon era
• Largest geological division
• Indefinable time
• The Eocene, for one
• Vast time frame