Ranking timeline system

Does anyone know a good way to show when someone become a legend, ancient, Myths…. Like a system that show how long time it take for someone to become it. I want to create a ranking power system that show how powerful someone can get with time.

A example of this:

  • Hero – 50 year
  • Legend – 500 year
  • Ancient – 1000 year
  • Myths – 2000 year