epoch

epoch
    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
    

Epoch \Ep"och\ ([e^]p"[o^]k or [=e]"p[o^]k; 277), n. [LL.
   epocha, Gr. 'epochh` check, stop, an epoch of a star, an
   historical epoch, fr. 'epe`chein to hold on, check; 'epi`
   upon + 'e`chein to have, hold; akin to Skr. sah to overpower,
   Goth. sigis victory, AS. sigor, sige, G. sieg: cf. F.
   ['e]poque. See {Scheme}.]
   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.
      [1913 Webster]

            In divers ages, . . . divers epochs of time were
            used.                                 --Usher.
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            Great epochs and crises in the kingdom of God.
                                                  --Trench.
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            The acquittal of the bishops was not the only event
            which makes the 30th of June, 1688, a great epoch in
            history.                              --Macaulay.
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   Note: Epochs mark the beginning of new historical periods,
         and dates are often numbered from them.
         [1913 Webster]

   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. "So
      vast an epoch of time." --F. Harrison.
      [1913 Webster]

            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.
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   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.
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            The long geological epoch which stored up the vast
            coal measures.                        --J. C.
                                                  Shairp.
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   4. (Astron.)
      (a) The date at which a planet or comet has a longitude or
          position.
      (b) 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.

   Syn: Era; time; date; period; age.

   Usage: {Epoch}, {Era}. We speak of the era of the
          Reformation, when we think of it as a period, during
          which a new order of things prevailed; so also, the
          era of good feeling, etc. Had we been thinking of the
          time as marked by certain great events, or as a period
          in which great results were effected, we should have
          called the times when these events happened epochs,
          and the whole period an epoch.
          [1913 Webster]

                The capture of Constantinople is an epoch in the
                history of Mahometanism; but the flight of
                Mahomet is its era.               --C. J. Smith.
          [1913 Webster]
    

epoch
 n.

   [Unix: prob.: 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
   U.S. 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}. Microsoft Windows, on the
   other hand, has an epoch problem every 49.7 days -- but this is seldom
   noticed as Windows is almost incapable of staying up continuously for
   that long.
    

epoch

   1. <operating system> (Probably from astronomical timekeeping)
   A term used originally in {Unix} documentation for the time
   and date corresponding to zero in an {operating system}'s
   {clock} and {timestamp} values.

   Under most Unix versions the epoch is 1970-01-01 00:00:00 GMT;
   under {VMS}, it's 1858-11-17 00:00:00 (the base date of the US
   Naval Observatory's ephemerides); on a {Macintosh}, it's
   1904-01-01 00:00:00.

   System time is measured in seconds or {ticks} 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 0.1 * 2**31-1 seconds, or 6.8 years.
   The one-tick-per-second clock of Unix is good only until
   2038-01-18, assuming at least some software continues to
   consider it signed and that word lengths don't increase by
   then.  See also {wall time}.

   2. <editor> (Epoch) A version of {GNU Emacs} for the {X Window
   System} from {NCSA}.

   [{Jargon File}]

   (2004-06-10)
    

20 Moby Thesaurus words for "epoch":
      Bronze Age, Dark Ages, Depression Era, Golden Age, Ice Age,
      Iron Age, Jacksonian Age, Middle Ages, New Deal Era,
      Prohibition Era, Silver Age, Steel Age, Stone Age, age, days, era,
      glacial epoch, interval, term, time