If your phone is not set to automatically retrieve datetime data from the server then you could manually select the time zone that is corresponding to the region that you are in.
For example if you live in Japan, then your correct time zone would be GMT +09:00, Japan Standard Time.
Here's how to change it:
1. Press the Home key.
2. Choose Settings.
3. Select Date and Time.
4. On the next screen untick the checkbox Automatic to ensure that it is not selected.
5. Now tap on Select time zone.
6. Finally choose your desire timezone.