Time zones started in the US at noon on Sunday, 18 November 1883, when American and Canadian railroads replaced an estimated 80 railroad times with four standard times one hour apart. Several cities heard noon twice that day, the Day of Two Noons. Congress made standard time federal law 35 years later, on 19 March 1918.
Key takeaways
- Before 1883, towns set clocks by the sun, which gave North America more than 144 local times and an estimated 80 railroad time standards, according to the Library of Congress.
- At noon on 18 November 1883, US and Canadian railroads switched to the mean times of the 75th, 90th, 105th and 120th meridians west of Greenwich, one hour apart.
- Credit is contested: Charles Dowd proposed hourly zones in 1870, Sandford Fleming argued for a worldwide 24-hour system from 1876, and William F. Allen wrote the plan the railroads adopted.
- The 1884 International Meridian Conference in Washington chose Greenwich as the prime meridian by 22 votes to 1, with 2 abstentions; it did not draw time zones.
- The Standard Time Act of 19 March 1918 put zones into federal law; US law now lists nine zones, with boundaries set by the Secretary of Transportation.
When did time zones start in the US?
US time zones began with the railroads, not the government: at noon on Sunday, 18 November 1883, railroad clocks across the United States and Canada were reset to a new standard. Federal law followed in 1918.
NIST puts it plainly: the US railroad industry set up a Standard Railway Time System on 18 November 1883, ahead of any international agreement, and most cities adopted it. William F. Allen, who organized the switch, told the 1884 Washington conference that the railroads of the United States and the Dominion of Canada had adopted the mean local times of the 75th, 90th, 105th and 120th meridians west of Greenwich. Those four meridians are the ancestors of Eastern, Central, Mountain and Pacific time.
How did people tell time before 1883?
Before standard time, each town kept its own local mean solar time, so noon came when the sun crossed that town’s meridian. The Library of Congress counts more than 144 local times in North America in the late 1800s.
Railroads layered their own times on top: an estimated 80 railroad time standards by the early 1880s, usually the time of a home city or a major city on the line. Passengers and station staff had to track several clocks at once.
Local newspapers show what the change meant. In Springfield, Illinois, the Illinois State Journal noted that the city’s railroad time, Chicago time, ran 8 minutes and 47 seconds ahead of the new standard, and reported that railroad office clocks would be set to the new standard at noon on the Sunday of the switch, NPR Illinois found in the paper’s November 1883 issues.
Who invented standard time zones: Dowd, Fleming or Allen?
No single person invented time zones, and credit is still contested: Charles F. Dowd proposed the idea, Sandford Fleming pushed for a worldwide system, and William F. Allen turned it into the railroads’ working plan.
| Person | What they did | Source |
|---|---|---|
| Charles F. Dowd | 1870 pamphlet proposing four zones one hour apart; he presented it to railroad officials but struggled to get it approved | Library of Congress |
| Sandford Fleming, Canadian railway engineer | 1876 memoir Terrestrial Time, proposing a worldwide standard on a 24-hour clock; delegate for Canada at the 1884 conference | Library of Congress; 1884 protocols |
| Cleveland Abbe, US meteorologist | Pressed for standard time to improve weather forecasting; a Committee on Standard Time formed at his urging in 1879 | Library of Congress |
| William F. Allen, secretary of the General Time Convention | Drew on Dowd, Fleming and Abbe; railroad managers voted for his plan in Chicago on 11 October 1883 | Library of Congress |
How the credit is told depends on where you read it. McGill University’s archives say Fleming is known as the Father of Standard Time, and The Canadian Encyclopedia calls him instrumental in convening the 1884 conference. The Library of Congress traces the idea from Dowd’s 1870 pamphlet to the plan Allen actually got adopted. All of these are fair; they describe different steps.
What happened at noon on 18 November 1883?
At noon on 18 November 1883, railroad clocks were reset to the new standard time, and in several cities noon sounded twice: once by the old local time, and again by the new standard. That is why the day is remembered as the Day of Two Noons.
The Library of Congress describes the preparation: railroad officials lobbied city governments, newspapers printed instructions and zone maps, and the US Naval Observatory and the Allegheny Observatory in Pittsburgh sent telegraph time signals so clocks could be synchronized. Most cities adopted the new time at once and others within a year, though NIST notes the change stirred local controversy for nearly a decade.
Allen’s own count, given at the 1884 conference, shows how far clocks moved:
| City | Old local time vs the new standard |
|---|---|
| Portland, Maine | 19 minutes faster |
| Atlanta, Georgia | 22 minutes faster |
| Omaha, Nebraska | 24 minutes slower |
| Houston, Texas | 24 minutes slower |
| Ellsworth, Maine | changed by 26 minutes |
By October 1884, Allen reported, nearly 85% of US cities with more than 10,000 people had adopted standard time for all purposes, and it ran on 97.5% of railway miles.
What did the 1884 International Meridian Conference decide?
The International Meridian Conference, which met in Washington from 1 October 1884 at the invitation of the US President, chose the meridian through the Greenwich observatory as the world’s prime meridian for longitude. It did not create time zones.
Its Final Act records the Greenwich vote as 22 in favor and 1 against (San Domingo), with Brazil and France abstaining. The conference also proposed a universal day: a mean solar day starting at mean midnight at Greenwich and counted from zero to 24 hours, without interfering with local or other standard time where desirable. Fleming spoke for Canada as a delegate of Great Britain, and Allen sat with the US delegation. Fleming linked the two subjects in one line: “To my mind, longitude and time are so related that they are practically inseparable.”
What did the Standard Time Act of 1918 do?
The Standard Time Act of 19 March 1918 (40 Stat. 450) wrote standard time zones into federal law, 35 years after the railroads’ switch, and gave the Interstate Commerce Commission authority over zone boundaries, the Library of Congress explains. The same act introduced daylight saving time, which was repealed after World War I.
The law lives on as 15 U.S.C. § 261, amended over the years including by the Uniform Time Act of 1966. It now divides the United States and its territories into nine zones, measured from Coordinated Universal Time, with boundaries defined by the Secretary of Transportation.
How far is clock noon from solar noon?
Clock noon and solar noon match only near a zone’s central meridian. A zone is about 15 degrees of longitude wide, so most places sit east or west of it, and the sun’s noon drifts through the year as well, by up to about a quarter of an hour either way.
Owaves is in Encinitas, California, at about 117.3 degrees west, east of Pacific time’s 120th meridian. On Pacific Standard Time, from early November to mid-March, solar noon in Encinitas comes between about half an hour before 12:00 on the clock and just after it, by the NOAA Solar Calculator. On daylight time the clock reads an hour later, so solar noon lands roughly half an hour to an hour after 12:00.
Your body clock tracks light, not railroad agreements. The NIH’s National Institute of General Medical Sciences says light and dark have the biggest influence on circadian rhythms. In a 2007 survey of more than 21,000 Germans, all on one time zone, sleep timing in smaller towns followed the local sun more than the official clock, while big-city residents’ timing tracked the clock more closely. It was an observational survey, so it shows an association.
Your day on My BodyClock
The day above on My BodyClock is planned around the sun rather than the railroad’s 12:00: wake at 6:30 AM, a daylight walk, breakfast, a train commute, focused work, lunch near solar noon, an outdoor break in the afternoon, the train home, an early dinner, time with family, then dim lights and lights-out at 10:30 PM. Every hour has a block, from Sleep to Flow.
Look up solar noon where you live, then build the day in Owaves: My BodyClock on the App Store or join the Android waitlist. Not sure when you naturally peak? Take the Body Clock Type quiz. More on light and timing: Let There Be Light When the Time Is Right, World Mental Health Day: Light, Rhythm and Your Mind, Caffeine Cutoff Time: When to Have Your Last Coffee and Beyond Willpower: Why Circadian Structure is the Next Frontier in Student Flourishing.
FAQ
Why is it called the Day of Two Noons?
On 18 November 1883, railroad clocks were reset to standard time at noon, and in several cities noon sounded twice: once by the old local time and once by the new standard. Places east of their zone’s meridian set clocks back, so they lived part of the late morning over again.
Did the government create US time zones?
Not at first. Railroads adopted standard time on their own in 1883, and Congress made it law only with the Standard Time Act of 19 March 1918. Zone boundaries are now set by the Secretary of Transportation under 15 U.S.C. § 261.
Who is called the father of standard time?
Canadian sources, including McGill University’s archives, call Sandford Fleming the Father of Standard Time. American accounts credit Charles Dowd with the first zone plan in 1870 and William F. Allen with the plan the railroads adopted in 1883, so the title is contested.
Did the 1884 Meridian Conference create the world’s time zones?
No. It chose Greenwich as the prime meridian and proposed a universal day starting at Greenwich midnight. Countries adopted zone time on their own schedules afterward.
How many time zones does the US have?
US law lists nine standard time zones, from 4 hours behind Coordinated Universal Time to 10 hours ahead of it, covering the states and US territories. The 1883 railroad system used four across the contiguous states.
Sources
- Charlotte Milliken (posted by Jennifer González). Whose Time Is It Anyway? A Brief History of Standardized Time Zones in the United States. In Custodia Legis, Law Library of Congress, 1 November 2024. https://blogs.loc.gov/law/2024/11/whose-time-is-it-anyway-a-brief-history-of-standardized-time-zones-in-the-united-states/
- International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day, October 1884: Protocols of the Proceedings (Gutenberg edition). https://www.gutenberg.org/cache/epub/17759/pg17759-images.html
- NIST Time and Frequency Division. A Walk Through Time: World Time Scales. https://www.nist.gov/pml/time-and-frequency-division/popular-links/walk-through-time/walk-through-time-world-time-scales
- NIST Time and Frequency Division. Time and Frequency from A to Z: Time Zone. https://www.nist.gov/pml/time-and-frequency-division/popular-links/time-frequency-z/time-and-frequency-z-ti
- 15 U.S. Code § 261, Zones for standard time (from Act of 19 March 1918, ch. 24, 40 Stat. 450). Legal Information Institute, Cornell Law School. https://www.law.cornell.edu/uscode/text/15/261
- Tara McClellan McAndrew. History: The Move Toward Standardized Timekeeping. NPR Illinois, 8 March 2017. https://www.nprillinois.org/illinois/2017-03-08/history-the-move-toward-standardized-timekeeping
- The Canadian Encyclopedia. Sir Sandford Fleming. https://www.thecanadianencyclopedia.ca/en/article/sir-sandford-fleming
- McGill University Archival Collections. Fleming, Sandford, 1827-1915. https://archivalcollections.library.mcgill.ca/index.php/fleming-sandford-1827-1915
- Roenneberg T, Kumar CJ, Merrow M. The human circadian clock entrains to sun time. Current Biology 17(2):R44-R45, 23 January 2007. https://doi.org/10.1016/j.cub.2006.12.011
- Bora Zivkovic. Sun Time is the Real Time. A Blog Around the Clock, Scientific American, 2007. https://www.scientificamerican.com/blog/a-blog-around-the-clock/sun-time-is-the-real-time
- National Institute of General Medical Sciences, NIH. Circadian Rhythms. https://www.nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms
- NOAA Global Monitoring Laboratory. NOAA Solar Calculator. https://gml.noaa.gov/grad/solcalc/
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