Timekeeping [Was: Re: cvs commit: src/usr.bin/vmstat vmstat.c src/usr.bin/w w.c]

Poul-Henning Kamp phk at phk.freebsd.dk
Sat Oct 22 02:48:39 PDT 2005

In message <20051022185422.Q8268 at delplex.bde.org>, Bruce Evans writes:

>What's a UTC delta?  Deltas don't (shouldn't) depend on the calendar.

As easy as it would be to stick our head in the sand, ignore
international treaties,geophysics and astronomy, point to POSIX and
ignore leapseconds, it is not an feasible way out for us as an
operating system project.

UTC deltas does depend on the calendar for now.

There is proposal from USA to make them DTRT pending in ITU-R Working
Party 7A, but it is meeting fierce opposition from astronomers and
geophysicists who hold the position that we can just ignore computers

Until the future of leapseconds are resolved, something that could
easily take 25 years, we have to deal with them.

So an UTC offect contains any leap seconds we are aware off, and
consequently, it depends on the calendar.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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