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The Encyclopedia of Horology

Watch family · Complication

World Time Watches

Partially verified

Watches displaying the current time in multiple time zones simultaneously, typically via a rotating 24-hour ring and a fixed or rotating ring of city names.

Movement & mechanism

  • A rotating 24-hour disc geared to complete one revolution per 24 hours, read against a fixed city ring (or vice versa)
  • A separate mechanism to advance the city/hour ring correctly relative to the main time display
  • Often combined with a day/night indication for the reference city

Identification

  • A ring of city names around the dial's outer edge
  • A 24-hour scale, often on a rotating inner ring, allowing all city times to be read simultaneously

Terminology

  • Cottier system — the influential world-time mechanism developed by Louis Cottier

Known variations

  • City-ring world timer
  • GMT-based simplified world timer

Pocket-watch ancestry

World-time functions have some precedent in pocket watches made for travellers and diplomats, but the fully developed rotating-ring world-time complication as commonly known today is principally a wristwatch-era development from the 1930s.

Collecting notes

Vintage world-time watches by makers using the Cottier mechanism are highly regarded in complicated-watch collecting for both mechanical and dial-design interest.

Photographs

Escapement Time Pilot Flieger Chronograph
Escapement Time Pilot Flieger Chronograph — Francis Flinch, CC0. Wikimedia Commons file page
Escapement Time Pilot Flieger Chronograph (cropped and turned 0.5*Pi)
Escapement Time Pilot Flieger Chronograph (cropped and turned 0.5*Pi) — Francis Flinch, CC0. Wikimedia Commons file page

Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.

Sources & references

  1. General horological literature on Louis Cottier's world-time mechanism.

Where sources disagree, the disagreement is stated rather than resolved silently.