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

[Paul Eggert]

On 06/24/2014 02:10 PM, Paul_Koning at Dell.com wrote:
> UTC, yes.  UT?

UT a.k.a. Universal Time" is deliberately ambiguous: it refers to all 
the UTx variants together.  Technically, GMT can refer to either a civil 
day (day starts at midnight) or an astronomical day (day starts at 
noon), and UT avoids this twelve-hour ambiguity by standardizing on the 
civil day.  Until 1952 the US Naval Observatory attempted to resolve the 
ambiguity by using the term "Greenwich Civil Time" (GCT) for civil-day 
GMT but that terminology did not catch on widely (it wasn't used in 
Britain), whereas UT has.