2014-04-26 10:52:28 -04:00
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epoch
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2014-04-26 11:54:15 -04:00
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n. [Unix: prob.: from astronomical timekeeping] The time and date
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corresponding to 0 in an operating system's clock and timestamp values.
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Under most Unix versions the epoch is 00:00:00 GMT, January 1, 1970; under
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VMS, it's 00:00:00 of November 17, 1858 (base date of the U.S. Naval
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Observatory's ephemerides); on a Macintosh, it's the midnight beginning
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2014-07-26 03:53:53 -04:00
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January 1 1904. System time is measured in seconds or ticks past the epoch.
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2014-04-26 11:54:15 -04:00
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Weird problems may ensue when the clock wraps around (see wrap around ),
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which is not necessarily a rare event; on systems counting 10 ticks per
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second, a signed 32-bit count of ticks is good only for 6.8 years. The
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1-tick-per-second clock of Unix is good only until January 18, 2038,
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assuming at least some software continues to consider it signed and that
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word lengths don't increase by then. See also wall time. Microsoft Windows,
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on the other hand, has an epoch problem every 49.7 days but this is seldom
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noticed as Windows is almost incapable of staying up continuously for that
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long.
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