On this night in science
The day of two noons
November 18, 1883
On this day in 1883, the railroads across the United States set their clocks to just a few shared time zones. Before then, many towns kept their own time by the sun, so in some places the clocks struck noon twice that day, once by the old time and once by the new.
Why it mattered
With shared time zones, a train schedule meant the same thing in every town along the line. The time zones we use today grew from that day.
Wonder together
If every town set its own clock by the sun, how would you know when to catch a train?