tz

from The Free On-line Dictionary of Computing (8 July 2008)

TZ

   <operating system> The {Unix} {environment variable}
   containing the current {time zone} identifier, e.g. "GMT",
   "EST".

   In early versions of Unix this variable simply contained the
   standard identifier for the zone, an offset in hours from GMT
   and an identifier to use during daylight saving time
   (e.g. "GMT0BST").  In later systems it stores the name of a
   file containing the details of a particular zone such as the
   dates when DST is in force.

   {Unix manual page}: ctime(3V).

   (1997-07-20)

from The Free On-line Dictionary of Computing (8 July 2008)

tz

   <networking> The {country code} for Tanzania.

   (1999-01-27)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

TZ
       Time Zone (Internet, TZ)