use Time::Zone;
print tz2zone();
print tz2zone($ENV{'TZ'});
print tz2zone($ENV{'TZ'}, time());
print tz2zone($ENV{'TZ'}, undef, $isdst);
$offset = tz_local_offset();
$offset = tz_offset($TZ);
"tz2zone()" parses the TZ environment variable and returns a timezone string suitable for inclusion in date(1)-like output. It opionally takes a timezone string, a time, and a is-dst flag.
"tz_local_offset()" determins the offset from GMT time in seconds. It only does the calculation once.
"tz_offset()" determines the offset from GMT in seconds of a specified timezone.
"tz_name()" determines the name of the timezone based on its offset