Here is a bit simpler way to get the timezone offset for the device using a Code/Javascript column.
The use case I can think of is that if you allow anyone to schedule things and they are in different time zones, you would save both the date/time as well as the timezone offset when the user creates the event. This way you can always calculate the events’ time shown in the user’s time, by doing some math with the saved timezone offset of the event and the current users’ timezone offset.
return (new Date().getTimezoneOffset())/60
