Timezone function - is this a good way around timezones?

[zeroblitzt]

function fixtime($oldtime)
{
$tz = $u['timezone'];
if ($tz || isset($tz))
{
$tz2 = ($tz * 60 * 60);
$newtime = $oldtime + $tz2;
return $newtime;
}
else
{
return $oldtime;
}
}

 

I have that function above, and my intent is to wrap that function around anything that comes out of the database of my website (messages, user sign up date, etc.). But I'm wondering if there is an easier way, or if this wont work.