Related Clues:

• Spans of history
• See 11-Across
• Important historic times
• Crosses
• Distinctive time periods
• Period pieces
• Concerns for Clemens and Rivera
• Time and time again?
• Extended periods
• See 50-Down
• Paleozoic and Cenozoic
• Key times in history
• Chronology sections
• Memorable times
• Swing and Gaslight