In 1883 we all got on board on November 18

 

On this day in 1883, 4 time zones simplified the country's railroad schedules and put cross-country friendships on track.

Here’s the story with some interesting links.
http://history1800s.about.com/od/railroadbuilding/fl/Why-We-Have-Time-Zones.htm

If you're a history buff, this is a very interesting site which will keep you wandering for a long time.