Re: [Gnu-arch-users] s/GMT/UTC/

[Jan Hudec]

On Tue, Sep 07, 2004 at 02:00:17 +0100, Andrew Suffield wrote:
> On Tue, Sep 07, 2004 at 08:14:29AM +1000, Zenaan Harkness wrote:
> > UTC is the newer name for GMT (actually, technically I thik they're
> > slightly different times, but anyway...).
> 
> UTC is basically the world trying to deny that timezones originate in
> Greenwich by renaming it. Political correctness gone completely insane.

No, they are defined differently.
(However, UT1 is what was called GMT before (and most people keep
calling it GMT)).

> > My recommendation is to use UTC rather than GMT. It's more accurately
> > defined.
> 
> This is not true. It is differently defined, but no more
> accurately. It is also unsupported by unix platforms, and anything
> else based on time_t; they really give you GMT and call it UTC

Right. time_t excludes leap seconds, so it really tracks GMT.

But at any point in time, GMT and UTC differ by at most 0.9s, and since
time_t precision is 1s, it can be considered the same.

> (inexplicably). It's actually off by a few seconds. UTC is not
> reliably defined in the future; you cannot say with precision what
> time it will be in one million seconds, other than "one million
> seconds from now"; there is no definition of how many seconds will be
> in a given year until that year occurs.

UTC inserts leap seconds, so the date counter can't be easily converted
to seconds. GMT on the other hand stretches the seconds, so the interval
corresponding to some number of seconds is not defined.

The article at:
http://www.ucolick.org/~sla/leapsecs/onlinebib.html
contains some discussion of how POSIX time and NTP time should be viewed
and concludes, that it's appropriate to consider them UT, that is GMT,
rather than UTC.

Thus I would vote for NOT changing the timezone specification to UTC.

-------------------------------------------------------------------------------
                                                 Jan 'Bulb' Hudec 
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