Related Clues:
- Geological span
- Geologic divisions
- History unit
- Major time periods
- It's comprised of ages and ages
- An extremely long time
- Heck of a long time
- Really big span
- Years and years on end
- Unimaginably long time
- Long time division
- Long times to wait
- Geological time span
- Span longer than an era
- Exceedingly long time