Flamsteed Astronomy Society

The Bureau des Longitudes, Paris

ó April 3, 2006

So lets have a look at the chronological sequence.


The Washington Conference of September/ October 1884 established Universal Time as mean solar time on the meridian of the transit telescope at Greenwich. In principle, it was possible to find UT at any place by observing local time (from the stars) and offsetting by the longitude difference of that place from Greenwich. With the development of radio time signals in the early 20th Century, it was found that time signals from remote locations could differ by a few seconds.


This could have been caused by a combination of several possible errors - uncertaintity in the precise longitude of a place, variations in Earth rotation speed, and polar axis wobble among them.


In 1912 the Bureau des Longitudes suggested international coordination of Universal Time and convened a conference with 19 countries participating. The proposals had not been ratified when the First World War broke out and delayed everything.


In 1919, the newly-formed International Astronomical Union had been formed and took responsibility for the BIH to implement the resolutions of the 1912 conference, brought up to date. The IAU used the Bureau des Longitudes and Paris Observatory offices to implement the decisions.


Note that although the ROG existed on the International meridian which defined time, the British Board of Longitude had been disbanded in 1828. Because the French had the organisational and institutional infrastructure already in place, they got the home for coordinatiing UTC.

1667†† Observatoire de Paris founded

1675†† Royal Observatory Greenwich founded

1714†† Longitude Act with £20000 prize

1766†† Nautical Almanac first published

1773†† Harrison awarded longitude prize for H4

1795†† Bureau des Longitudes founded in Paris

1828†† British Board of Longitude disbanded

1854†† Bureau des Longitude mission extended to include geodesy and time standardisation.

1884†† Washington Conference establishes GMT as Universal Time

1912†† Paris conference sets up Commission Internationale de líheure and the BIH

1919†† CIH and BIH ratified and set up within existing structure of Paris Observatory and Bureau des Longitude under the International Astronomical Union

1956†† Organisational authority for BIH transferred to the Federation of Astronomical and Geophysical Sciences

1984†† Unification of terrestrial reference frames : ITRF and WGS84

1988†† BIPM took responsibility for TAI and all associated activities.

IERS to coordinate ITRF to ICRF based at Paris Observatory.




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