conversion- heure anglaise or Greenwich time 1892

GMT is the name given to MEAN SOLAR TIME at the Greenwich meridian; it is the popular name for civil time kept in the UK. The need for a standard time across the country came with the development of the railways, from 1825 onwards. 

For example, passengers travelling from Bristol to London would find a ten-minute difference between the time kept in the two cities because local time, measured according to the position of the Sun in the sky, varies with longitude. Eventually the railways adopted Greenwich time, which became known as ‘railway time’, as their standard and in 1880 it became the legal time for the whole country.

Maps with multiple meridians were confusing

 In 1928 the INTERNATIONAL ASTRONOMICAL UNION (IAU) recommended that Greenwich Mean Time should become the Standard timescale for scientific purposes and be known as UNIVERSAL TIME (UT).

A bit of history. For older history click here 

England adopted the Greenwich time (GMT) on the 13th January 1843.

Greenwich Mean Time was adopted across the island of G. B. by the Railway in 1847.

London adopted Greenwich time January I3, I848, for the official use of the entire nation. 

Obviously such a plan would not work in the United. States. They gave up on the quixotic notion that the world revolved around Washington and adopted Greenwich time as early as 1850 the United States by Act of Congress.

 It was gradually adopted for other purposes, but a legal case in 1858 held "local mean time" to be the official time. This changed in 1880, when GMT was legally adopted throughout the island of Great Britain.

 Ireland as part of UK adopted Greenwich Mean Time in 1916

To learn about other places, let's state three cases:

 Earlier in Europe there were 20 prime meridians. Finally, 128 years ago 41 delegates from 25 nations gathered in Washington in the US for the 1884 International Meridian Conference to decide from where time and space should be measured. 

By the end of the difficult summit, fumatta bianca, dragged on until "smoke came out", Greenwich had won the prize of longitude 0º by a vote of 22 to one, with only San Domingo against and France and Brazil abstaining. BBC news

But in 1911 times were far form standardised.

Luigi Barzini wrote about Belgium in the winter 1911:

In 1911 Belgium alone had adopted l'heure anglaise or Greenwich time, which was 9 minutes behind Paris time, 4 minutes behind French railway time, and 20 minutes behind Ductch time. The Europeans (1983)

France legalised the official Greenwich time in March 1911, Portugal January 1912.

Bruxelles, 1892 (the invention of new traditions)

Madrid, 1940 (a political criteria)

Beijing, 1992 (China country follows the Capital time zone since 1949, although the 5 time fuses were in use since 1912)

Bruxelles, 1892 (the invention of new traditions): Mayor Charles Buls says no

The municipalities of the Brussels region resisted long time. During the session of the City Council of Brussels of 11 April 1892, mayor Charles Buls strongly opposed to the introduction of the GMT. He based himself on several arguments: the disturbance of the biorhythm of the human beings, the time difference being ridiculously small because of the small surface of Belgium, and the English time that did not interest Belgium. These arguments were fought by scientific proofs during the same session.

New hour for schools and administrations

Other bordering municipalities of Brussels discussed the question as well. The municipal administration of Saint-Gilles was the first to accept the introduction of the Greenwich Mean Time, on 16 March 1892. The municipality of Laeken gave in after a long debate. The municipal administration of Schaerbeek was to follow. Finally the law of 29 April 1892 was passed in Belgium. From 1 May 1892 the GMT was applied on the whole Belgian territory. The leaders of the schools of Laeken received a 'service order' on 30 April 1892.

Ville de Bruxelles nouvelle: l'adoption, en 1892, de l'heure du méridien de Greenwich par Bruxelles et Laeken.

Inimaginable, mais jusqu'en 1892, pour prendre le train d’Ostende à Verviers par exemple, il fallait avancer les aiguilles de sa montre dans chaque ville où le train s’arrêtait. Une réalité quotidienne pour les voyageurs belges et étrangers au 19e siècle. Pour en finir avec ce désordre horaire, la solution était d'uniformiser les horaires en passant à l'heure du méridien de Greenwich.

C’est pour cette raison que le Ministre belge des Chemins de fer, du Télégraphe et des Postes avait décidé en 1892 que l’heure légale pour les horaires des trains de l’Etat serait l’heure de Greenwich. L'Observatoire royal d’Uccle avait calculé qu’il fallait reculer les aiguilles de 17 minutes et 29 secondes par rapport à l’heure du méridien de Bruxelles.