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!