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Until the late nineteenth century, time in North America was a strictly local affair.

Each town set its clocks by the sun, declaring it noon when the sun stood highest in the sky.

Because the sun appears to travel westward, noon in Boston arrived roughly twelve minutes earlier than noon in New York, a difference that hardly mattered as long as nobody could travel between the two cities quickly.

The railroads changed all that.

A passenger heading west might pass through dozens of local times in a single journey, and timetables became bewilderingly complex.

Matters were made worse by the railroad companies themselves, each of which kept its own time; some large stations reportedly displayed several clocks, each showing a different hour.

Missed connections were the least of it: on single-track lines, a discrepancy of a few minutes could put two trains on a collision course.

The solution, when it finally came, was the work of the railroads rather than of any law.

Under a plan drawn up by William F. Allen, an engineer and editor of a railroad guide, the continent was carved into zones exactly one hour apart.

On November 18, 1883, station clocks across the country were reset.

In cities where local time ran a few minutes ahead of the new standard, clocks were turned back at noon, so that noon arrived twice.

Not everyone took kindly to the change.

Some towns dug in their heels and kept local time for years, and critics grumbled that railroads had no business dictating the hour.

Yet the logic of the timetable proved hard to argue with.

Within a generation, standard time had become so ingrained that most people forgot it had ever been invented at all.