"It is extremely complicated though unless you know every visitor to your site is in the same part of the world, to work properly you would have to get them to input their latitude and longditude and correct current timezone and have access to forumulas which will calculate sunrise and sunset times for everywhere around the world - not an easy task."

No, actually it would be possible to do something like visualtraceroute.datametrics.org on a couple of packets. Using that info it could customize it. It could also ask for the users time zone and customize it for each user.