Epoch

Ep´och Pronunciation: ĕp´ǒk or ē´pǒk; 277

n.	1.	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. In divers ages, . . . divers epochs of time were used. - Usher. Great epochs and crises in the kingdom of God. - Trench. The acquittal of the bishops was not the only event which makes the 30th of June, 1688, a great epoch in history. - Macaulay.
	2.	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. The influence of Chaucer continued to live even during the dreary interval which separates from one another two important epochs of our literary history. - A. W. Ward.
	3.	(Geol.) A division of time characterized by the prevalence of similar conditions of the earth; commonly a minor division or part of a period. The long geological epoch which stored up the vast coal measures. - J. C. Shairp.
	4.	(Astron.) The date at which a planet or comet has a longitude or position. The capture of Constantinople is an epoch in the history of Mahometanism; but the flight of Mahomet is its era. - C. J. Smith.

Noun	1.	epoch - a period marked by distinctive character or reckoned from a fixed point or event Synonyms: era
	2.	epoch - (astronomy) the precise date that is the point of reference for which information (as coordinates of a celestial body) is referred Synonyms: date of reference
	3.	epoch - a unit of geological time

1.		epoch - [Unix: probably from astronomical timekeeping] The time and date corresponding to 0 in an operating system's clock and timestamp values. Under most Unix versions the epoch is 00:00:00 GMT, January 1, 1970; under VMS, it's 00:00:00 of November 17, 1858 (base date of the US Naval Observatory's ephemerides); on a Macintosh, it's the midnight beginning January 1 1904. System time is measured in seconds or tick s past the epoch. Weird problems may ensue when the clock wraps around (see wrap around), which is not necessarily a rare event; on systems counting 10 ticks per second, a signed 32-bit count of ticks is good only for 6.8 years. The 1-tick-per-second clock of Unix is good only until January 18, 2038, assuming at least some software continues to consider it signed and that word lengths don't increase by then. See also wall time.
2.		epoch - (Epoch) A version of GNU Emacs for the X Window System from NCSA.