A hardware device that needs to be told what timezone it is from a mobile app.
The hardware then tracks log data in specified timezones, and logs it to a file.
The app sends this data periodically to an API in utc format.
And the app needs to visualise the data, but offset to the timezone they are currently in, whilst maintaining the data of a day in the timezone(s) they where originally logged, based on the configured settings which may change at any given time