Editing Time signal (section)

=== United States ===
Telegraph signals were used regularly for time coordination by the [[United States Naval Observatory]] starting in 1865.<ref>{{Cite web |url=http://tycho.usno.navy.mil/history.html |title=Timekeeping at the U.S. Naval Observatory |access-date=10 April 2018 |archive-date=19 December 2017 |archive-url=https://web.archive.org/web/20171219093942/http://tycho.usno.navy.mil/history.html |url-status=dead }}</ref> By the late 1800s, many U.S. observatories were selling accurate time by offering a regional time signal service.<ref>{{cite book |last=Bartky |first=Ian R. |date=2000 |title=Selling the true time |url=https://archive.org/details/sellingtruetimen00bart_0 |url-access=registration |publisher=Stanford University Press |page=[https://archive.org/details/sellingtruetimen00bart_0/page/199 199] |isbn=9780804738743 |access-date=29 March 2019 }}</ref>

[[Sandford Fleming]] proposed a single 24-hour clock for the entire world. At a meeting of the Royal Canadian Institute on 8 February 1879 he linked it to the [[Prime meridian (Greenwich)|anti-meridian of Greenwich]] (now 180°). He suggested that standard [[time zone]]s could be used locally, but they were subordinate to his single world time.

[[File:Standard Time from Ladd Observatory.png|thumb|Advertisement for a telegraph time signal service (1900)]]
[[Standard time]] came into existence in the United States on 18 November 1883.  Earlier, on 11 October 1883, the General Time Convention, forerunner to the [[American Railway Association]], approved a plan that divided the United States into several [[time zone]]s.  On that November day, the US Naval Observatory telegraphed a signal that coordinated noon at Eastern standard time with 11&nbsp;am Central, 10&nbsp;am Mountain, and 9&nbsp;am Pacific standard time.

A March 1905 issue of ''The Technical World'' describes the role of the United States Naval Observatory as a source of time signals:

:''One of the most important functions of the Naval Observatory is found in the daily distribution of the correct time to every portion of the United States. This is effected by means of telegraphic signals, which are sent out from Washington at noon daily, except Sundays. The original object of this time service was to furnish mariners in the seaboard cities with the means of regulating their chronometers; but, like many another governmental activity, its scope has gradually broadened until it has become of general usefulness. The electrical impulse which goes forth from the Observatory at noon each day, now sets or regulates automatically more than 70,000 clocks located in all parts of the United States, and also serves, in each of the larger cities of the country, to release a time-ball located on some lofty building of central location. The dropping of the time-ball – accompanied, at some points, with the simultaneous firing of a cannon – is the signal for the regulation by hand of hundreds of other clocks and watches in the vicinity.''