World time

A world-time display pairs a ring of place names, one for each time zone, with a rotating hour or 24-hour ring, so the time in any listed place can be read off directly. The British Museum holds an early example (museum number 1958,1201.907), a lever movement and dial of about 1860 described as a "MOVEMENT AND DIAL OF A LEVER WATCH WITH WORLD TIME INDICATION" with a "rotating white enamel minute ring" and a "cream enamel outer ring with hours for 25 European cities", GREENWICH set at XII. Its curatorial comments record that "the dial design was patented in England by Modeste Anquetin on March 17th 1857".

The reason one ring can work is that civil time is organised in zones counted from a single meridian. Royal Museums Greenwich records that at the 1884 conference in Washington delegates "voted to make the Greenwich Meridian the world's Prime Meridian" and "also recommended a new global time zone system based on Greenwich Mean Time". How many names a maker puts on the ring is its own choice, not a standard: the 1857 dial carries 25.

The open question is attribution. The modern world-time wristwatch layout is usually credited to the Geneva watchmaker Louis Cottier. This Codex could not verify that from the museum record it cites here: the British Museum record names Modeste Anquetin, Droz, Soldano and Beguelin, and not Cottier, and the accounts that do name him are enthusiast media, which this Codex does not cite. What is documented is that a dial of this kind was patented in England in 1857, some seventy years earlier.