Related Clues:

• Roaring Twenties, e.g.
• Many chiliads
• Time period
• See 49-Across
• A long, long time
• Use a stopwatch
• Stretch of history
• Part of B.C.E.
• Ready for plucking
• The Thatcher years, e.g., in Britain
• Immeasurable period
• Loooong wait
• Astronomical periods
• Laundry detergent brand
• Historic time