Just joking. Try setting a wider sleep hours on your device - for example from noon to noon (minus a minute) or from midnight to midnight (minus a minute). Or change the sleep time range each time you change the time zone. Also when changing the TZ, it is safer to re-sync the clock with the help of GPS (turning on an outdoor activity untill it acquires the satellites), and then rebooting the watch.
My watch sincs with my phone, so the time shows correctly. How do I change the estimated sleep time range on the app? I sleep from about 04:00am-14:00pm.
The watch takes the time from GPS, not from the phone app, AFAIK, though it is possible that it varies by model. To be sure that all internal timers are correctly set, I'd turn on the GPS and reboot, after each change of TZ. I saw already several posts of people here on the forum complaining about diverse problems related to time, after changing their TZ. Usually the acquiring the GPS and rebooting the watch helped, hence the recommendation. However, it is possible it is unnecessary in your case.
How do I change the estimated sleep time range on the app?
It is in Device Settings » User Settings. You can go through the app, but you can change it direcltly on the watch too. Where exactly, depends on your model. If you do not find it, look up the adequate User Manual, for the steps relevant for your watch.
