Related Clues:

• Geological time period (Var.)
• Stretches of history
• Improves, as whiskey
• Nears retirement
• Some sentence units
• 25 B.C. and 1978, e.g.
• 1 billion years
• Day divisions
• Important periods
• A billion years (Var.)
• 365 billion days, astronomically
• Interminable stretch
• '-- Flux' (1995 TV series)
• They may be checked at the door
• Almost eternity