Patek Philippe is once again producing a World Time wristwatch. I was very pleased to learn that the craftsmen at Patek did not find it sufficient to simply reproduce their previous complication. Instead, Patek has pushed the technology further, with exclusive innovations, creating an even more alluring piece. This is a truly new watch, designed not for collectors to stash away in their safe, but actually for world travelers, with considerations of form and function.
The Patek Philippe World Time, Ref. 5110, tells the time in 24 cities, and can be instantly adjusted to reflect a new local time without affecting the minutes.
In the watch pictured, the home city is Paris, where it it 10:09 am. The hands show 10:09 as with a normal watch. On the black and silver middle 24 hour ring, 10 is at 12 o'clock, on a silver background, indicating daylight hours. The sun is at 12pm in the silver part of the 24 hour ring, with the moon at 12 midnight.
It is 9 minutes past midnight in Anchorage Alaska, and 9 past noon in Moscow. See how easy it is!
The middle ring rotates counter clockwise as the minute hand moves clockwise. All of the cities adjacent to the black part of the middle ring are experiencing darkness (ignoring daylight savings and the variability of sunrise and sunset).
Click on picture for larger image: 
This middle ring is the key element of the worldtime design invented by watchmaker superstar Louis Cottier (1894-1966) in the 1930s.
This simplicity of this operation is reflected in the complexity of the movement, the new automatic Calibre 240/188.
In the 5110, a single push button allows the wearer to select a home city, which changes three things on the face: The hour hand jumps forward to reflect the new time, the outer ring displaying the cities jumps counter clockwise to put the new city at 12, along with the 24 hour middle ring.
Calibre function details from Patek Philippe: Three wheels (G, H & I) control the 24-hour disc, city disc and hour hands and are permanently fixed to each other. They are linked to the minute wheel via a clutch mechanism which, while engaged, provides drive for the three indications equally. The clutch, which originally saw the light of day in Patek Philippe's 1959 patent for the Travel Time, allows the mechanism to be momentarily disengaged for the fraction of time required for the double function corrector (D) to come into play. The secret to the world Time’s precision lies in the process controlling the correction of the different indications. The centre wheel (G) is fitted with dents de loup (wolf's teeth) which allows for changes to be made in 'all or nothing' stages. As wheel G is corrected so are the 24 disc (via wheel H) and the hour hand (via wheel I). The impulse from wheel (I) follows through to the time zone wheel and the local hour wheel (J). As the clutch re-engages the hour wheel falls into alignment with the minute hand. Key: A. The 24 hour disc, driven from wheel (H) and shows the local time at each city on disc (B). B. The city disc, remains static during normal running. C. The Hour hand, controlled by wheel (K) during normal running. D. The pusher activates the correcting lever at (F). E. The dial; naturally kept as simple as possible. F. Double function corrector; provides the impulse to move the city disc one step anti-clockwise and advances wheel (G). G. The 'wolf's teeth' wheel is so fitted as to allow 'all-or-nothing' impulse from (F). It is permanently linked to wheels (H) and (I). H. Controls the 24 hour disc (A). I. Transfers the impetus from (F) to correct the hour hand via the time zone wheel (K). J. The hour wheel; linked to both the minute wheel and wheel (K), it incorporates the clutch mechanism that disengages momentarily, allowing the minute wheel to continue without interruption when wheel (K) is advanced. K. The time zone wheel; normally controlled by (J), it in turn controls the hour hand. It can be corrected by wheel (I).
Copyright 2000, Cormac Kinney and ThePuristS.com
