Related Clues:
- Eon divisions, in geology
- Many are named for presidents
- Pitching staff stats
- How many times Bob Marley will "Do It"?
- They are historical
- Careful way to think
- Significant parts of history
- Big Band and Victorian, for two
- Gaslight and Big Band
- Christian and Prohibition, for two
- Periods in history books
- Some are named after presidents
- Documentary divisions
- The Roaring Twenties and others
- Paleozoic, Mesozoic and Cenozoic