That's one way to do it in winter, if exactly 12 hour days suffice, and don't move too much. Manually adjusting the longitude every time I fly to the US would b

That's one way to do it in winter, if exactly 12 hour days suffice, and don't move too much. Manually adjusting the longitude every time I fly to the US would be a pain though. What I'd really like is to tell it 'turn yourself off at sunrise, turn yourself on at sunset or 2100, whichever's later'.