n. - 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.
n. - A period of time, longer or shorter, remarkable for events of great subsequent influence; a memorable period; as, the epoch of maritime discovery, or of the Reformation.
n. - A division of time characterized by the prevalence of similar conditions of the earth; commonly a minor division or part of a period.
n. - The date at which a planet or comet has a longitude or position.
n. - An arbitrary fixed date, for which the elements used in computing the place of a planet, or other heavenly body, at any other date, are given; as, the epoch of Mars; lunar elements for the epoch March 1st, 1860.