Related Clues:

• What a houseguest's stay might feel like
• History book topic
• Astronomer's time period
• The Modern, for one
• Memorable time span
• Years of note, collectively
• Long time period
• Long interval
• Bold shelfmate
• The Swing, for example
• 1,000,000,000 years
• One billion years, in geologic time
• Victorian or Napoleonic
• Waiting period, it sometimes seems
• Disco, for one