Skin temperature overnight messages store how the skin temperature measured during the night deviates from the personal baseline of the user.
timestampDateTimeMoment the message refers to, in UTC. FIT stores it as seconds since the FIT epoch (December 31, 1989, 00:00:00 UTC); decoders usually expose it as a regular date.
localTimestampLocalDateTimeSame instant as the timestamp, but expressed in local time. The difference between both gives the UTC offset (time zone and daylight saving time) at the time of recording.
averageDeviationFloat32Average deviation from the baseline over the night, in degrees Celsius.
average7DayDeviationFloat32Average deviation from the baseline over the last 7 nights, in degrees Celsius.
nightlyValueFloat32Overnight skin temperature.
mesgNumStringGlobal message number identifying the kind of message. Decoders use it to know which profile to apply to the data.