To reset the time correctly when you change time zone, press the re-set button ( see number 5 below) with a pin. Then power on the watch by holding the silver button for about 3 seconds (see number 3 below). It may take a few minutes for the watch to find the mobile signal if you are indoors or you may need to be at a window or outside for the watch to pick up the signal.
The time will show correctly within a few of minutes once the watch locates a signal. The time may initially reset incorrectly by 1 hour before the time sets correctly. In some cases, if the time resets incorrectly and has not corrected within 5 minutes, you may need to reset a 2nd time. You will not lose any information or settings by pressing the reset button.