Hello @wojtech
Thanks for posting about this.
It sounds like your timezone may not be set correctly. We use your account's timezone to determine start time for activities that do not contain GPS information (indoor, workouts, swims, etc.). Please try the following:
- Access your account through the Strava Website
- Go to Profile > Settings
- Select your current location and type in Los Angeles & Save (this is to reset the time zone, we recognize this is not your accurate location. You will reset your location in step 5)

- Select Refresh Page

- Enter in your correct location & Save.
- Select Refresh Page (if the time zone still does not refresh to match your location please try step 3 again and then refresh the page followed to ensure the time zone and location match. Then enter your correct location again and refresh the time zone). Sometimes the timezone gets stuck and just needs to get adjusted back and forth to reset itself. Once it is set and is accurate it will not revert back.
Please work through those steps. This will not correct start times for previously uploaded activities, but should resolve the problem for future activities.