How to add / substract an hour from current time?

I want to implement a dual time field on my watchface. Was thinking of allowing users to select the timezone, ie +1, +2, +3, -1, -2, -3 from the clockClock using something like this:

var oneHour = new Time.Duration(3600);
var dualTime = clockTime + oneHour;

But this doesn't work. Any help on the best way to achieve this would be greatly appreciated!

Thanks.