Local time / GMT display from data field

I have the CRM system that I built from scratch. One of the lines that I need to display is the time of the next appointment. It's a piece of cake to get it done for the users local time zone. I'm using this code:


date ("@ G:i T ", strtotime ($row_activeContactsRS['nxtTime']));

This is displaying like this:

Next Appointment: 10/19/12 at: @ 12:30 PDT (just the bold part)
1PDT[/B] (just the bold part)

What I want to display is :

Next Appointment: 10/19/12 at: @ 12:30 PDT / 19:30 GMT

Any ideas???

Use the datetime objects. Much easy:

date_default_timezone_set('UTC');

$dt = new DateTime($row_activeContactRS['nxtTime']);
$tzUTC = new DateTimeZone('UTC');
$tzPDT = new DateTimeZone('PDT');

print $dt->format('m/d/y @ G:i T') . PHP_EOL;
$dt->setTimezone($tzUTC);
print $dt->format('m/d/y @ G:i T') . PHP_EOL;

That's a good start. However, this just brought up a bigger problem. Users are going to be all over the world so I've got to derive their local time zone, let them enter the time as a local time zone value, store it as GMT. Storing as GMT is the only way that the local time will be correct. I'll have to find a script that will take a local time entry from a text field and convert it to GMT, then read the GMT back as local time for any user in any part of the world.