Pierre Lamy wrote:
UTC aka Coordinated Universal Time, is the "right now is right now for
all of us" time, and is coordinated among several entities, irregardless
of the timezone the parties are in. GMT is a timezone with an offset of
zero. All timezones are differentials off of UTC; you couldn't just say
that in parts of England, you don't have a timezone - everyone has a
timezone. So GMT exists with an offset of zero.
Actually, GMT is not just a time zone with an offset to UTC. Read e.g.
Langley's short document describing UTC and GMT [1], and hopefully you will
see what I mean.
For a list of time zones have a look at [2], note the 15th time zone.
See also the section on time zones in Markus Kuhn's [3] document on ISO 8601.
To some people it's just semantics, to others it has great importance.
In general usage it is identical to use GMT over UTC. But since there are
two possible meanings for GMT differing by up to 0.9 seconds [1] I think it
is important the output from 'date -u' is in UTC as that is what the date(1)
says.
Also, I find the following behaviour to be inconsequent
23:06~$ ls -l /etc/localtime
lrwxr-xr-x 1 root wheel 23 Jun 1 20:25 /etc/localtime ->
/usr/share/zoneinfo/UTC
23:07~$ date
Thu Apr 12 23:07:23 UTC 2007
23:07~$ date -u
Thu Apr 12 23:07:25 GMT 2007
[1] http://gauss.gge.unb.ca/GMT.UT.and.the.RGO.txt
[2] http://en.wikipedia.org/wiki/List_of_time_zones
[3] http://www.cl.cam.ac.uk/~mgk25/time/
/Markus
