Out in Dunhuang in western China, it's still fairly bright out at 10 o'clock at night, thanks to the fact that there's only one time zone in the entire country—everyone is synched to Beijing time. No one I've talked to here seems to mind; freakishly late sunsets are just a fact of life. (The one exception is in the autonomous Xinjiang region in the far west, where people wake up for work two hours later.) And when I try to explain the logic behind multiple time zones, I realize I have no real idea why, say, the U.S. approach is superior.
As it turns out, Tim Harford looked into this question a few years back. Basically, there's a trade-off between coordination and sunlight. In the United States, each time zone gets to experience sunrise and sunset in the same way, but there are coordination problems—bankers in San Francisco have to get up at 5 a.m. to keep up with Wall Street, which forces local coffeeshops and so on to open extra early (and out of synch with the rest of the city). In China, meanwhile, everyone in the country is in synch with each other, but some people get screwy daylight schedules.
So which is preferable? One economic study on television schedules suggests that our sleeping patterns are affected far more by our need to synch up with other time zones than by when the sun rises and sets. When daylight savings pushes TV schedules up or down in some states, lots of people will adjust their slumber habits, while shifts in daylight hardly have any effect at all. That's not conclusive, but it does suggest we value coordination more than set sunlight patterns. Maybe there's something to be said for a unified time zone. It is awfully disorienting, though.
(Flickr photo credit: tayofj)