I'd recommend the calendar app as well. It's as simple as touching the complication and will probably give you a better viewpoint of your day/week than time travel could ever achieve.
The reason time travel can't do this is pretty simple; appointments/calendar is not the only complication. The only scenario Apple could implement this would be if the appointment complication were the ONLY complication (that implements time travel) on the watch face. Otherwise it would screw with the other complications. And in this case it's debatable if that confuses things by changing time travel functionality depending on which set of complications are being displayed.
I suppose one potential implementation would be to increment by "complication changes" instead of by minute. I could possibly see that working better anyway, because who needs to see minute-by-minute updates really....
(obviously this was an evolving post... haha)