This passage was written for this guide. It discusses how a standardized system of clock time developed during the nineteenth century.
For most of human history, the correct time was a local matter. A town read the hour from the sun: noon arrived when the sun stood highest over the church steeple or the market square, and every community a few miles east or west reached that moment a little sooner or later. Two towns fifty miles apart might set their clocks eight or ten minutes apart and think nothing of it, because there was rarely any reason for the two towns to compare. Time was something the sky handed down, not something people negotiated. The railway changed that — and in changing it, revealed that the right time was less a fact of astronomy than an agreement among strangers who needed to coordinate.
The trouble began with the timetable. A stagecoach that took most of a day to cross a county could tolerate a ten-minute disagreement between the clocks at either end; a locomotive covering the same ground in an hour could not. When each station along a line kept its own sun time, a printed schedule became a puzzle. Passengers missed connections that had, by their own watches, not yet departed. Worse, on the single tracks that carried trains in both directions, dispatchers timed the movements of oncoming trains by the clock. If the clocks disagreed, two trains could be released toward each other in the confident belief that the line was clear. The margin between an ordinary crossing and a collision was measured in minutes, and minutes were exactly what the old system could not guarantee.
British railway companies found the obvious remedy first. Rather than reconcile dozens of local times, they simply ignored them. Beginning in the 1840s, the lines ran their trains on a single standard — the time kept at the Royal Observatory in Greenwich — and hung railway time on the walls of their stations. At first this created an odd double life: a station clock might show one hour while the clock on the town hall across the street showed another. But the railway's version was too convenient to resist, and over the following decades British towns quietly abandoned their own noons in favour of Greenwich. What began as an internal convenience for one industry hardened, by 1880, into the legal time of the whole country.
North America posed a larger problem, because it was a larger place. A continent spanning many degrees of longitude could not sensibly keep a single clock; when the sun was overhead in New York it was still well short of noon in Chicago. Instead of one time, the American and Canadian railroads agreed on several. On a day in November 1883, the major lines carved the continent into a small number of broad zones, each roughly an hour apart, and reset their clocks to the new scheme. In many cities the change arrived as a brief, strange interruption — a day of two noons, when the clocks were stopped or turned back so that the old local time could hand off to the new standard. Crucially, no government had ordered this. The railroads, private companies acting in concert, had rewritten the nation's clocks because it was good business to do so.
The final step was international, and it too was a matter of agreement rather than discovery. In 1884 delegates from more than two dozen nations met in Washington for the International Meridian Conference. Their task was not to find the prime meridian — no such line exists in nature — but to choose one. After debate they settled on Greenwich, in part because so much of the world's shipping already used charts based on it. From that reference the globe could be divided into a tidy framework of zones, each defined by its distance from the agreed centre. The line through Greenwich was not more real than any other; it was simply the one the delegates consented to treat as real.
It is tempting to remember standard time as a discovery, as though someone had at last measured the hour correctly and told everyone else. But the sun had not changed, and no new instrument had been invented. What changed was that commerce — the railway above all — created a need for strangers in distant places to act on the same instant, and that need was met not by astronomy but by negotiation. The time on our clocks is a monument to a bargain.
