Related Clues:

• 15-Across, e.g.
• Tide competitor
• Piece of history
• Days of yore
• Bottom line?
• Distinctive time
• Cause for Steinem
• See 21-Down
• Generation
• Historical time to remember
• Proust's ''Remembrance of Things ---''
• See 40-Down
• It contains periods
• Big time
• Significant time period