Display time from other timezone

I am still working on packet analyzer I mentioned last time. Another problem to solve - capture happen in different timezone and I need to output correct time regardless of where my script is running.

The solution is quite simple, but took me few hours to figure out. I fairly quickly discovered that localtime behavior can be changed by setting timezone (TZ) environment variable. When set from command-line, everything worked, but when set from inside of script

$ENV{TZ} = 'GMT+7'

the time was for my timezone. Sometime later digging in POSIX library I got the idea that setting TZ in %ENV hash does not propagate to underlying C layer. Someone else has definitely similar problem, because CPAN module Env::C mention exactly that in its documentation.

This is what I end up with:

use POSIX qw(tzset); 
use Env::C;

Env::C::setenv('TZ','GMT+7',1);
tzset();

print scalar localtime(1289250253);  # Mon Nov  8 14:04:13 2010 everywhere