Events of the health data collection, as exposed to Garmin Health SDK applications.
Moment 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.
eventIdUint8Identifier of the event.
mesgNumStringGlobal message number identifying the kind of message. Decoders use it to know which profile to apply to the data.