Hi all-
The epoch affects many things so let's document it
even further. Jesus's latest commit (bug #22620) is
related. Sara added some good information in #21646.
One idea is to create a <note> entity named
¬e.timestamp; that *briefly* describes unix
timestamps including the windows limitation. This
entity will link to a section (or faq) that further
describes epoch and potential gotchas.
Do any other OS's disallow negative timestamps?
Every function that deals with epoch will include this
short note towards the bottom of the page. Maybe it
should simply be in the 'see also' versus a <note>?
Thoughts?
Regards,
Philip
p.s. from the jargon files:
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.
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