The time displayed on your Pulse HR is based on the time of your mobile device. The tracker can display the time in 24-hour format. To change the time display of the tracker, go to the Settings of your smartphone before configuring or syncing the Pulse HR with the Withings App. 

If you ever have to change time zones while wearing your Pulse HR, all you have to do is open the Withings App to sync your tracker with your device and the correct time will be displayed.

Note that you won’t have to worry about daylight savings either. In this case as well, syncing your Pulse HR with your device will be enough to update to the correct time.