Manage date as UTC

Hi there,

I'm setting up a website that provide access/translation for different regions.

The system should show users the same date/time, example:
User 1 is from USA, Washington (GMT-5) -> 2th Jan, 13:30
User 2 is form Australia, Canberra (GMT+11) -> 3th Jan, 05:30

I want to show GMT+0 (18:30) -> 2th Jan, 13:30 for all users.

And I want avoid DLS changes. I've read that there are 2 GMT types:
- GMT as UTC (no DLS changes) - I want this
- GMT as region (DLS changes)


Now, in CodeIgniter, what I should do to collect that? I see in config.php an option ($config['time_reference'] = 'local'.
I should change it or not? And that change give me chances to show the same date/time to all users?

I know, I'm newbie here, but if you have simple practice example on how-to-do it as best practice, would be perfect.

Thank you all!