Related Clues:
- Vast age
- Inordinately long time
- Important historical period
- About 525 trillion minutes, in astronomy
- Uncountable years
- Astronomical time span
- Eocene, e.g.
- Umpteen years
- Forever, more or less
- Historical stretch
- Vast time span
- Oligocene, for one
- 365 billion days, geologically
- Big stretch?
- Long geological span