How can I reset my watch back one hour.

Your Apple Watch picks up the time from your iPhone. The iPhone time is determined by Settings > General > Date & Time. For most of us, that is set automatically but you can turn that off and manually change the time zone. This, however, will change the time on both your watch and iPhone.

I guess the answer would be based on why you want to do this. Does it have to do with time zones or daylight savings time? If so that should be automatic. Your iPhone knows where it is and adjust the time based on its location.