[kijin]

Yes, it would require either a GPS or a manual setting of the location. I also imagine it's going to be incredibly difficult to process the kinds of trigonometric formulae that length-of-day and twilight calculations involve, using only mechanical gears.

On the other hand, Japanese watchmakers don't seem to be particularly averse to mixing analog with digital, mechanical with electronic. So I wouldn't be surprised if Citizen, for example, came up with a hybrid GPS/mechanical watch that does exactly what the Apple Watch does while the Swiss toil for decades trying to build a purely mechanical version.