Re: [LEAPSECS] making leap hours workable

From: <ut1-mail_at_ASTHE.COM>
Date: Wed, 2 Jul 2003 20:32:18 GMT

> The second reality is that many existing applications depend on calculations
> that assume that time_t has exactly 86400 seconds per year. (Note that it
> does NOT follow from this that there are 86400 POSIX seconds in any given
> calendar year. ...

Obviously you mean "per day".

> UTC+TZ is the only
> readily available precise measure of local time, so mandating TAI would
> conflict with this.

I beg to differ on your use of "precise measure". Nothing in POSIX requires
time (local, time_t, etc.) to be precise.

Correct me if I am wrong, but:

    Timezones in POSIX are defined as offsets of the "UTC timezone"
    (sic) as P1003.1 once called it. Names of points in time within the "UTC
    timezone" are computed from those "seconds since the Epoch" timestamp /
    time_t values.

    Nothing in POSIX, as far as I can see, says that "PST8PDT" has anything
    to do with UTC, local standard time, TAI, etc. It is a 8 hour offset
    from that "UTC timezone" which related to those "seconds since the Epoch"
    timestamp values / time_t values. And as you point out:

> POSIX implementors and application writers ... have no control over
> whether time_t is TAI, UTC, or anything else. This is under the control of
> the system owners and operators, and the host environment that the POSIX
> implementation is embedded in.

.. the time_t can be anything ... including TAI, UTC, a bogus clock, etc.

    * So time_t can be related to almost anything.

    * The POSIX "TZ=UTC" names computed from those seconds since the Epoch"
      time_t timestamp values can therefore related to almost anything.

    * Timezones such as "PST8PDT" are 8 hours off of POSIX "TZ=UTC",
      can therefore related to almost anything.

And thus the claim of "mandating TAI would conflict with this" appears
to be false.

=-=

I am not commenting on the value/wisdom of "mandating TAI". But from
my reading of POSIX, it appears that there is no POSIX conflict in
"mandating TAI".

chongo () /\oo/\

=-=

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Received on Wed Jul 02 2003 - 13:35:23 PDT