Geological Eras

Era:                     Years after 1950(?) it began:


Cenozoic                 65,000,000 years ago


Mesozoic                250,000,000


Paleozoic                540,000,000


Neoprotozoic          900,000,000


Mesoprotozoic      1,000,000,000     


Paleoprotozoic      2,500,000,000


Archaean              3,880,000,000


Hadean                 4,500,000,000


Each of these Eras may be divided into Periods. Cenozoic may be too young to have Periods.


I am pretty sure that most of these Eras belong to the Phanerozoic Eon.