I have the same issue for running activities and I think it has gone out after the last software update on my watch.
The activities show the right date and day but in the news feed they are a day out.
Weird as the individual activities are correct, it is just the news feed that is wrong.
Hello all-
For anyone who is experiencing this date discrepancy, could you please post a screenshot showing the differing dates in the activity/news feed? Additionally, please answer the questions below:
Here’s a screen shot of my news feed showing an activity incorrectly as “Thursday” and an activity shot showing it correctly as 8 Dec being Wednesday. Note that I am in the New Zealand time zone.
Yes, you can email and access my Garmin connect account 
