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

[John Meinel]

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.
My understanding was it was *Coordinated* Universal Time. Meaning they 
take more than one atomic clock, average the results, and call that UTC, 
rather than GMT which is only one clock.

> > 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
> (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.
>
> It's not really the most sensible way to describe time.

Actually, it may not be the most *sensible*, but it is the most 
*accurate*. Because of leap seconds. Basically, it does not take exactly 
365 1/4 days to go around the sun, and I believe the earth doesn't 
rotate exactly 24 hours. So every so often (very rarely, though), a 
minute will have 61 seconds instead of 60. See here:
http://tycho.usno.navy.mil/leapsec.html

If you read through it, you will see where the need arose. Basically, we 
have atomic clocks that count one second very regularly, but the earth 
doesn't rotate, nor revolves around the sun with the same regularity. To 
make January 1st, 0:01 correspond to the same location around the sun, 
we have to make adjustments here and there.

I could say we should change time to not be so Earth-centric, but since 
we all live here for now, we'll probably be okay for at least all of my 
lifetime.

John
=:->

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