Converting a user submitted date to GMT

Code igniter 2.x

I need to convert a form filled date and time and time zone to GMT

User submits a date field like 7/2/2015

Time field like 8:00 PM

and a timezone like: UM5

I found this page: https://ellislab.com/codeigniter/user-gu...elper.html

But I am still not sure how to go about this.

Thank you for your time.

Randy