Related Clues:
- It's longer than an era
- Big time division
- Span of epoch proportions?
- G permits them all
- Extensive period
- Immeasurable time
- Billion-year time period
- Gets old
- One billion years, geologically
- Grows more antiquated
- All ___ (words on a game box)
- Humongous span
- Times of your life?
- Annoying wait, facetiously
- Particular periods