This isnt just an issue with my 955, but has always happened on my Edge 530 as well, but has become more obvious since using things like Morning Report.
In Garmin Connect I have the Upload TimeZone set, and all exercises have always uploaded correctly, into the correct timezone
In Garmin Connect I will have a training plan loaded up with workouts most days. All workouts display in Garmin Connect as they should on the correct day.
If I go into "Training Plan" on the Edge530 it will show correctly the list of workouts and the correct day (eg Zone 2 Aerobic 15 Feb 2025). However, if I go into the Calendar on my 955, it shows the same workout, but a day later (Zone 2 Aerobic on the 16 Feb).
Aside from the 955 showing the incorrect day, the annoyance comes when you start an exercise session, and get the prompt for todays workout. On both the 955 and 530 it always prompts for yesterdays workout ... almost as thought its being forced to treat the day as US time (since NZ is GMT+12).
Same occurs on the 955 with morning report. In the "workout for the day" section, its always showing yesterdays planned workout.
Given this occurs across multiple garmin devices, Im thinking its a setting in Garmin Connect somewhere, or Garmin is just US Centric and doesnt work for those of us in the Southern Hemisphere :)