Related Clues:

• Nonspecific duration
• Quite a stretch
• Eternities
• Vast expanse of time
• Lotsa time
• Geologic time unit
• 365 billion days, in astronomy
• Several eras
• It's quite a stretch
• Oodles of time
• Incredibly long time
• Proterozoic or Archeozoic, e.g.
• Period of many years
• Extremely long time
• Long periods