It would be really interesting to study this - in Europe the same time-zone covers between approximately 30m behind true time (e.g. in eastern Poland) and 1h 30m ahead (in Galicia) - do Galicians typically get up later than Poles?

China has it even more so - a single time-zone covering what should be five - are people in Fuyuan waking up at 03:00 when the sun rises in summer, whilst people in Zanda sleep in till 07:30?