The International Meridian Conference

Each nation counted longitude from its own meridian. Bencker, writing in 1945 for the International Hydrographic Bureau, notes that a congress called by Richelieu fixed the meridian of Ferro for France in 1634, and that France later used the Paris meridian for national purposes as Britain used Greenwich.⁴

Britain had already put Greenwich time into law: the Statutes (Definition of Time) Act, given royal assent on 2 August 1880, made Greenwich mean time the legal time of Great Britain and Dublin mean time that of Ireland.^6, 7

Bencker records that Sandford Fleming proposed unifying time in 1879 and that the International Geodetic Congress at Rome in 1883 recommended one meridian for all countries; the Library of Congress dates Fleming’s Terrestrial Time to 1876.^4, 8

In North America the railroads had changed to standard time on 18 November 1883, on zones counted from meridians west of Greenwich.^1, 8, 9

Called at the invitation of President Chester A. Arthur, the conference opened on 1 October 1884 in the Diplomatic Hall of the State Department, with Rear-Admiral C. R. P. Rodgers of the United States as its president; Wikipedia counts 26 countries and 41 delegates.^1, 2

On 2 October the delegates agreed without dissent that a single prime meridian for all nations was desirable. France asked for a meridian of absolute neutrality, cutting no great continent; on 13 October that proposal was lost by 21 votes to 3, Brazil, San Domingo and France voting for it.¹

The same day the conference voted for the meridian through the centre of the transit instrument at Greenwich, the meridian most of the world’s shipping already used for its charts, by 21 to 1: San Domingo voted against, and Brazil and France abstained. The Final Act of 22 October records 22 in favour, Salvador having joined.^1, 2, 3

The protocols record the French delegate Lefaivre saying France did not concur in Greenwich and arguing that it served commerce rather than science, and the Spanish delegate Valera accepting Greenwich in the hope that Britain and the United States would take up the metric system.¹

The conference also proposed a universal day, a mean solar day beginning for all the world at mean midnight on the initial meridian, for all purposes for which it might be convenient and without interfering with local or standard time. The universal day passed by 23 votes to none; its start at midnight by 15 to 2, with 7 abstaining.¹

Longitude was to be counted both ways from Greenwich up to 180 degrees, east plus and west minus, by 14 votes to 5, with 6 abstaining; a last resolution asked for technical studies of decimal division of angles and time.¹

The resolutions bound no one. Delegates said from the opening sessions that they could not commit their governments, and the Final Act proposed Greenwich to the governments represented rather than adopting it.¹

Whether the conference set up time zones is told differently. Its Final Act has no resolution on zones, and its universal day was not to interfere with local or standard time; Royal Museums Greenwich says the conference recommended a world system of zones based on Greenwich Mean Time, and Bencker that it advocated 24 zones.^1, 3, 4

In practice Greenwich became the reference for time as well as longitude: NIST describes zones that average 15 degrees, an hour apart, with boundaries adjusted to suit the people who live by them.⁹

Wikipedia’s account dates Japan’s standard time to an imperial ordinance of 13 July 1886, which made the 135th meridian east, nine hours ahead of Greenwich, the standard meridian from 1 January 1888.¹⁰

Germany made the mean solar time of the fifteenth meridian east of Greenwich its legal time by a law of 12 March 1893, in force from 1 April 1893.^5, 11

The German Wikipedia lists the same Central European time in Italy in 1893, Switzerland and Denmark in 1894, Norway in 1895 and Sweden in 1900; in Switzerland it became national time by custom and was put into law only in 1981.¹¹

France kept its own meridian. A law of 14 March 1891 made Paris mean time the legal time of the whole country; a law of 9 March 1911 set legal time at Paris mean time less 9 minutes 21 seconds, which is Greenwich time without naming Greenwich.^4, 12

Radio then carried the time. Regular time signals from the Eiffel Tower, controlled by the Paris Observatory, began on 23 May 1910; Bencker records that ships found the signals of different stations disagreeing, sometimes by a second.^4, 13

An international time conference met at the Paris Observatory from 15 to 23 October 1912, with 16 countries represented. It decided that radio time signals should be sent in universal time and set up an international time commission and the Bureau International de l’Heure, housed at the Observatory.^{4, 14, 15}