period, period of time, time period - an amount of time; "a time period of 30 years"; "hastened the period of time of his recovery"; "Picasso's blue period"

Caliphate - the era of Islam's ascendaancy from the death of Mohammed until the 13th century; some Moslems still maintain that the Moslem world must always have a calif as head of the community; "their goal was to reestablish the Caliphate"

Christian era, Common era - the time period beginning with the supposed year of Christ's birth

day - an era of existence or influence; "in the day of the dinosaurs"; "in the days of the Roman Empire"; "in the days of sailing ships"; "he was a successful pianist in his day"

age, historic period - an era of history having some distinctive feature; "we live in a litigious age"

modern era - the present or recent times

geologic time, geological time - the time of the physical formation and development of the earth (especially prior to human history)

Age of Mammals, Cenozoic, Cenozoic era - approximately the last 63 million years

Age of Reptiles, Mesozoic, Mesozoic era - from 230 million to 63 million years ago

Paleozoic, Paleozoic era - from 544 million to about 230 million years ago

eon, aeon - the longest division of geological time

geological period, period - a unit of geological time during which a system of rocks formed; "ganoid fishes swarmed during the earlier geological periods"