Select Menu > Settings and Date and time.
Change the time zone when traveling
Select Date & time settings > Time zone:.
Select the time zone of your location.
The time and date are set according to the time zone. This makes sure that your device displays the correct sending time of received text or multimedia messages.
For example, GMT -5 denotes the time zone for New York (USA), 5 hours west of Greenwich, London (UK).
See Set an alarm.