Related Clues:

• Exceedingly long time
• Long time span
• Long time, geologically
• It may be after lunch
• Long geological stretch
• A billion years, to Hubble
• Many many centuries
• Centuries of centuries
• Time pieces
• Dog's age
• Eternity, seemingly
• Long period of time
• A month of Sundays
• Prolonged period
• L-o-n-g stretch of time