Related Clues:

• Unique stretch in time
• "Ol!" for one
• Paleozoic, for example
• --- of Good Feelings
• Several periods
• Shout of praise
• Period piece?
• One hundred percent
• Jubilation
• ''Give me an A...,'' e.g.
• Nifty
• Important historic period
• Geological time period
• Important time span
• See 90-Across