age, era, period (of time) / the times, spirit of the age / antiquity / a time in one's life, one's days (in college etc.)

period drama

a historical period where social disorder is so great due to war, disease, political disorder etc. that there is little or no cultural development; Dark Ages

anachronism

youth (part of life following childhood)

zeitgeist (the spirit of the age)

Age of Enlightenment (period of history)

(archaeology) the Stone Age

new age; new era; new epoch; new period

(archaeology) the Iron Age