[tz] 'date -u' should say "UTC", not "GMT"

[Paul_Koning at dell.com]

On Jun 24, 2014, at 5:02 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:

> Come to think of it, the tz implementation of 'date -u' should say "UTC" instead of "GMT", and in general the tz code and documentation should prefer UT or UTC to GMT whenever this would improve technical accuracy.  Although "GMT" is the traditional time zone abbreviation output of 'date -u', POSIX has allowed "UTC" ever since IEEE Std 1003.1-1992.  Outputting "UTC" is more technically correct, certainly for time stamps since 1961, and arguably even before that if one interprets "UTC" proleptically.  Also, outputting "UTC" is now a quite-common behavior, since it's the standard behavior in GNU/Linux.  So I'll look into proposing a patch to the tz code to have it support this behavior.  There are probably a few other places in the code that should also prefer "UT" or "UTC" to "GMT".

UTC, yes.  UT?  I know of UT1 and UT2, but neither are the same as UTC and neither is applicable here.  

	paul