UNIVERSAL TIME
Universal time is a complication that allows the simultaneous display of the time across all 24-hour time zones. This complication first appeared in the late 19th century with the adoption of time zones (coordinated time). The Geneva-based watchmaker Louis Cottier became renowned for developing numerous Universal Time mechanisms, significantly contributing to its advancement.
In addition to local time, which is generally displayed on a 12-hour cycle at the centre, the outer edge of the dial features a 24-hour disc and a concentric ring displaying an emblematic city for each of the 24 time zones. Two different mechanisms exist to animate this complication.
In the first, the 24-hour disc rotates clockwise over 24 hours while the city disc remains fixed. The 24-hour markings move past the 24 time zones, allowing the wearer to read the time in all zones at any given moment.
In the second possible configuration, the 24-hour disc remains fixed while the city disc rotates counterclockwise over 24 hours.
Just like watches displaying two time zones, the setting of world time (relative to the local time shown at the centre) can be adjusted using a single pusher (or corrector). In such cases, the correction is performed by either incrementing or decrementing only.
Here again, some timepieces feature two pushers or two correctors to make adjustments. In this configuration, one is used to increment the corrected value, while the other is used to decrement it.
Finally, world time adjustment can also be carried out via the crown, depending on the construction. In this case, the correction may be unidirectional (incrementing or decrementing only) or bidirectional (both incrementing and decrementing).
