[CLUE-Talk] Uptime? [Fwd: Interesting definition of epoch from dictionary.com]

[Kevin Cullis]

Interesting issue.

Kevin


> 
> 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.