1840 – 1918
How did time zones start? Railway time and the 1884 Meridian Conference
Time zones started with the railways. British railways adopted London time in the 1840s, and on November 18, 1883 US and Canadian railroads switched to five standard zones. In 1884 the International Meridian Conference in Washington, D.C. chose Greenwich as the prime meridian. Each country then adopted zones by its own laws over the following decades.
Key facts
| Great Western Railway adopts London time | 1840 |
|---|---|
| GMT becomes legal time in Great Britain | 1880 |
| US and Canadian railroad standard time | November 18, 1883 ('the day of two noons') |
| International Meridian Conference | October 1884, Washington, D.C., 25 nations, 41 delegates |
| Vote for Greenwich | 22 in favour, 1 against (San Domingo), 2 abstentions (France, Brazil) |
| France switches from Paris time | 1911 |
| US time zones in federal law | Standard Time Act, 1918 |
Until the 1800s, time was local. Noon was when the sun was highest over your town, so clocks in Bristol ran about 10 minutes behind London, and in the US, Boston and New York differed by about 12 minutes. With travel at the speed of a horse, nobody noticed.
The trains changed everything
Railways made local time a real problem. A railway timetable with a different time for every station was confusing at best and, on single-track lines, dangerous. In Britain, the Great Western Railway began running on London time in 1840, and the Railway Clearing House recommended in 1847 that all companies follow. Telegraph signals from the Royal Observatory at Greenwich soon carried the time down the lines. Many towns adopted "railway time" for their own clocks, and Greenwich Mean Time became the legal time across Great Britain in 1880.
The United States, much wider, had dozens of railroad times. On Sunday, November 18, 1883, the railroads of the US and Canada switched to four standard zones across the US (Eastern, Central, Mountain and Pacific) plus an Intercolonial zone in the east of Canada, each a whole number of hours from Greenwich. Clocks in many cities were stopped or reset at noon, which is why it was called "the day of two noons." It was a private agreement between railroad companies; federal law didn't make it official until the Standard Time Act of 1918.
Several people had proposed zones before this. The Italian mathematician Quirico Filopanti described 24 hourly zones in 1858, the American school principal Charles F. Dowd promoted railroad zones from 1869, and the Canadian engineer Sandford Fleming campaigned from 1876 for a single worldwide system. The boundaries actually used in 1883 were drawn up by William F. Allen, editor of the Official Railway Guide. See who invented time zones.
The 1884 International Meridian Conference
In October 1884, 41 delegates from 25 nations met in Washington, D.C. to choose a single prime meridian for longitude and timekeeping. Greenwich was the practical choice: by then most of the world's shipping already used charts based on it. The vote was 22 to 1, with San Domingo against and France and Brazil abstaining. The conference also recommended a "universal day" counted from midnight at Greenwich.
One point is often misremembered: the conference did not create the world's time zones. It only chose the meridian. Countries adopted zones based on Greenwich one by one, by their own laws, over the next half-century. France kept Paris time until 1911, and then defined its legal time as Paris time minus 9 minutes 21 seconds, which happened to equal Greenwich time. The Netherlands used Amsterdam time, about 20 minutes ahead of Greenwich, until 1940.
From zones to daylight saving
Once clocks were standardized, governments could move them all at once. Germany and Austria-Hungary introduced daylight saving time in 1916 to save fuel during the First World War, and Britain, the US and others soon followed. The Standard Time Act of 1918 gave the US both its legal time zones and its first daylight saving time.
Today the system is maintained in a public database, the IANA time zone database, which records every zone's rules and history, and is what phones and computers use to set their clocks.
Questions people ask
When were time zones invented?
US and Canadian railroads introduced standard time zones on November 18, 1883. Britain had used a single national time, GMT, on its railways since the 1840s.
Did the 1884 conference create the 24 time zones?
No. It chose Greenwich as the prime meridian. Individual countries adopted time zones based on Greenwich later, by their own laws.
Why was Greenwich chosen as the prime meridian?
By 1884, about 70% of the world's shipping already used charts that measured longitude from Greenwich, so it was the least disruptive choice.
Sources
Last updated October 18, 2026. Found an error? Tell us.