We're using the Fitbit Inspire 2 as part of a research project on occupational and environmental health in Guatemala. Before each site visit, our team syncs and prepares the Fitbits in advance. Occasionally, our visits align with daylight savings time changes, so we make sure to update the devices to reflect the correct local time.
However, we’ve been noticing discrepancies in the data. Specifically, there is missing data between 5:00 AM and 10:00 AM, and in some cases, data appears to be recorded overnight—even though participants only wear the Fitbits between 5:00 AM and 4:00 PM.
Our main question is: when we export the data (e.g., as a .json file), what time zone are the timestamps in? Are they based on the local time at the time of collection, or is there a standardized time zone (e.g., UTC) that Fitbit uses regardless of location?
Additionally, what could be causing the missing data during the day and the unexpected data collected overnight?
Moderator edit - updated subject for clarity
