Epoch : (noun)
1: a period marked by distinctive character or reckoned from a
fixed point or event [syn: era]
2: (astronomy) the precise date that is the point of reference
for which information (as coordinates of a celestial body)
is referred [syn: date of reference]
3: a unit of geological time
Based on WordNet 2.0
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Epoch : \Ep"och\ (?; 277), n. [LL. epocha, Gr. ? check, stop, an
epoch of a star, an historical epoch, fr. ? to hold on,
check; 'epi` upon _ ? 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.
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.
Note: Epochs mark the beginning of new historical periods,
and dates are often numbered from them.
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.
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.)
(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.
The capture of Constantinople is an epoch in the
history of Mahometanism; but the flight of
Mahomet is its era. --C. J. Smith.
Based on Webster's Revised Unabridged Dictionary
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Epoch :
1. (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. (Epoch) A version of GNU Emacs for the X Window
System from NCSA.
[{Jargon File]
(2004-06-10)
Based on the Online Dictionary of Computing [Computer_Dictionary]:
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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 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 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.
Based on the Online Dictionary of Computing [Computer_Dictionary]:
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