I was having the same issue and called Garmin support. They had me sync the time with GPS and that fixed the incorrect sunrise/sundown issue.
As there are still complains about the incorrect data by some minutes or even hours, I doublechecked what my F5+ delivers. Interestingly there is a slight difference between the Garmin widget and 3rd party…
As there are still complains about the incorrect data by some minutes or even hours, I doublechecked what my F5+ delivers. Interestingly there is a slight difference between the Garmin widget and 3rd party connect iq apps and some other sources of data.
Data on the F5+
Garmin Widget: 7:48 16:21
Sun & Moon times widget 7:50 16:20
Watchface SC8 7:50 16:20
Other sources:
WetterOnline 7:50 16:18
Google 7:51 16:19
LunaSolCal (Android App) 7:49 16:19
Everything is related to the position of the last GPS-Fix! Sometimes I can see the sunset from my office and it also fits to the sunset-alert of my watch. So far I only used this watch at different locations within Germany and the data were always correct within differences as shown above. I am going to visit a different time-zone in December and I hope this will also work. My previous watches (Fenix 1 and 3) worked perfectly in that aspect!
I just come back from UK and there also sunrise and sunset were accurate after the first GPS-fix, which I did already in the plane to adjust to the local time.
I did a run in Cambridge before work and used the track navigation, everything perfect!
Hold the Set button and then scroll until you get to "Set Tmie With GPS" Push the GPS button to sync time with GPS.