Downloaded data from Google Takeout is not what the phone app shows for same day and time.
Example heart rate data from Google Takeout for one day is not the same as the app displays.
Additionally the watch is off my wrist once or twice a day, the app shows not data for those times, while downloaded data for same day and time shows data.
Left watch off my wrist for 24 hour period, the downloaded date contains date for the 24 hour period but the app data is blank.
Google Takeout data uses UTC timestamps and this was corrected to local time, as the app shows, using spreadsheet software.
