I have basic understanding on Time related stuff. Every Unix system has epoch time in seconds that is number of elapsed seconds since 1 Jan 1900 GMT. Your machine or server adjusts time with different offsets (+ or - in seconds) based on the geography. If you have observed, to get the IST we add +5:30 on GMT time to get the correct time.
If your servers are located in different geographies and you are providing service at a particular location then you to have manipulate time accordingly. In Diameter protocol so many AVP are Time type and Time is represented in GMT/UTC.
There are numbers of online time converters are available.
Reference:
http://www.epochconverter.com/timezones?q=**********&tz=UTC