The problem is in the "time_offset" field in the "device_settings" message in the FIT file generated from a watch app.
The time_offset value is correct with a positive time zone but it is corrupt when the time zone is negative.
To replicate
A. to show it works with a positive time zone:
Create an Activity file from a watch app in a time zone east of the Prime Meridian, i.e. with a positive time zone.
I tested in Sydney (UTC+11).
Decode the FIT file with FitCSVTool.jar
Observe the device_settings time_offset field is correct.
I received the correct value of 36900 (11x60x60)
B. to see the error:
Re run in a time zone west of the prime meridian, i.e. a negative time zone, like USA CA (UTC + 8)
Decode the FIT file with FitCSVTool.jar
Observe the device_settings time_offset field is incorrect.
I expect time_offset,"-28800" (-8x60x60), I receive, time_offset,"4294938496",
It's not a problem with FitCSVTool:
I receive the same incorrect value with my FIT file decoder, so the problem is not within FitCSVTool.
The problem appears to be the way the negative time_offset is being generated.
Work-around:
The work around is to subtract 0x1000000 from the incorrect value.
