Epoch - Definition

n 1: a period marked by distinctive character or reckoned from a
fixed point or event [syn: era, epoch]
2: (astronomy) an arbitrarily fixed date that is the point in
time relative to which information (as coordinates of a
celestial body) is recorded [syn: epoch, date of
reference]
3: a unit of geological time that is a subdivision of a period
and is itself divided into ages