Loyal readers of this blog know that as you travel east or west, local time is determined by how far you are from the Prime Meridian. Each degree of longitude means 4 minutes of time difference. Wherever you happened to live in the United States in the 1800s, your town kept local time depending on when the Sun was highest—at noon. Your town’s time might be a few minutes different from the next town to the west or east.
That changed when the railroad connected the country.
Trains must keep to schedules! The boys in the railroad scheduling department didn’t want to pull out a sextant to know when the train would pull into the station in Grand Rapids or Medicine Hat or Lake Tahoe. They needed time to be simpler. So they dreamed up the idea of time zones.
“On November 18, 1883, America’s railroads began using a standard time system involving four time zones, Eastern, Central, Mountain and Pacific.”
That meant everybody in one time zone all kept the same time. If you travel over to the next time zone, you change your watch or clock by one full hour. A time zone represents 15° of longitude only roughly. Mostly it’s the states’ boundaries—not the actual meridian—that determine the split. If the state is too big to conveniently fit into 15 degrees, then county lines are used to define the time zone.
Back to the beginning of The Western Civ User’s Guide to Time & Space