a period marked by distinctive character or reckoned from a fixed point or event
source: WordNet 3.0
(astronomy) an arbitrarily fixed date that is the point in time relative to which information (as coordinates of a celestial body) is recorded
source: WordNet 3.0
a unit of geological time that is a subdivision of a period and is itself divided into ages
source: WordNet 3.0
A fixed point of time, established in history by the occurrence of some grand or remarkable event; a point of time marked by an event of great subsequent influence; as, the epoch of the creation; the birth of Christ was the epoch which gave rise to the Christian era.
