Source : Free On-Line Dictionary of Computing

tz
     
         The {country code} for Tanzania.
     
        (1999-01-27)

TZ
     
         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)