The "World Time 5330" was a Japan-exclusive model unveiled at the "Patek Philippe Watch Art Grand Exhibition (Tokyo 2023)." This wasn't just a recolor of an existing model; it featured a date display and a mechanism that moved in conjunction with the hour hand. In 2024, Patek Philippe released this model as a regular production item. Let's take a closer look at its mechanism.
Photographs by Eiichi Okuyama
Masamasa Hirota (this magazine), Yukiya Suzuki (this magazine): Interview and text
Text by Masayuki Hirota (Chronos-Japan)
Text & Edited by Yukiya Suzuki (Chronos-Japan)
Edited by Yuto Hosoda (Chronos-Japan)
[Article published in the July 2025 issue of Kronos Japan]
The date display is the real charm of the new World Time, now that it's a regular feature.
Many watch manufacturers now employ the Louis Cottier-style world timer. This involves marking the name of a city on the outer edge of the dial and using a rotating 24-hour ring to read the time in that location.
The Cal.240HU adds a world time mechanism to the masterpiece Cal.240. The Cal.240HU C, announced in 2023, further adds a pointer date. Although the basic design is old, the accuracy is extremely good. It uses ceramic ball bearings, but the rotor noise is also well suppressed. Despite the addition of a date display, the diameter increased by 3mm to 30.5mm and the thickness increased by 0.7mm to 4.58mm.
When Cottier developed this mechanism in 1931, top manufacturers such as Patek Philippe, Vacheron Constantin, Agassiz, and Breguet all began to adopt it. However, from a mechanical standpoint, Patek Philippe is arguably the one that creates the most advanced world time watches. The "World Time 5100," released in 2000, features a push button at the 10 o'clock position that moves not only the hour hand but also the city disc on the outer edge of the dial. This makes it easy to set the local time simply by pressing a button, even when traveling from Japan to the United States. To put it crudely, Patek Philippe's World Time is like combining Rolex's GMT mechanism, which allows you to quickly move the hour hand forward and backward with just the operation of the crown, with a world timer and linking it to the city display. There is probably no other world time watch on the market that is as easy to use.
The World Time 5330 now features a date display. Compared to the existing 5230, the diameter is 2.5mm larger and the thickness is about 1.5mm thicker, but it remains perfectly practical. In addition, the adoption of a transparent glass date display hand does not obstruct the legibility of the dial. Automatic movement (Cal.240 HU C). 37 jewels. 21,600 vibrations/hour. Power reserve of approximately 48 hours. 18K white gold case (40mm diameter, 11.57mm thickness). 3 ATM water resistance.
However, in 2023, Patek Philippe combined this outstanding World Time with a date display, and the following year, 2024, released it as the regular model "World Time 5330." The developer was Philippe Barra, head of the R&D department, who also developed the 2000 World Time. At first glance, this may seem like simply adding a date display to the existing World Time, but its realization was by no means easy.
As already mentioned, Patek Philippe's World Time watch has the unique feature of advancing the hour hand and city disc by one hour and one time zone when the push button at the 10 o'clock position is pressed. However, simply adding a date display to this would render it unusable. This is because if the date display is linked to the advancing hour hand and city disc, the date will also advance. In other words, if you keep pressing the button, only the date will keep changing.
Barra cited two challenges in the development process: "Finding the slimmest possible mechanism that would fit within the limited space of the existing world time mechanism, and solving the problem of the date remaining the same when crossing the International Date Line at midnight."
As the clock hands advance, the date display hand moves forward one day after midnight. Similarly, pressing the push button at the 10 o'clock position to advance the hour hand also advances the date display hand by one day. The problem arises when crossing the International Date Line. For example, suppose you take a flight from Haneda to Hawaii at 9:55 PM on June 10th. You will arrive at 4:55 AM on the 11th in Japan time, which is 9:55 AM on the 10th in Hawaii time. Because you cross the International Date Line, the date goes back one day to the 10th. On the other hand, if you press the button at the 10 o'clock position to set the city display at the 12 o'clock position to Hawaii, the hour hand also moves and the clock displays 9:55 AM. However, even if you cross the International Date Line, if the mechanism is the same as previous world time watches, the date cannot be reset.
Patek Philippe incorporated a solution where the date resets when crossing the International Date Line. Looking at the city display ring, there is a red dot on the city disc of the dial (between Oakland and Midway), which is the 180-degree longitude line, or the International Date Line.
When you press the push button, the hour hand advances every hour, and the date advances accordingly. However, when the city disc crosses the International Date Line at the 12 o'clock position, the date also resets. The hands advance the date, and the city disc resets it. This unprecedented idea was made possible by a differential gear (and an extremely compact one at that) placed at the center of the movement.
When the push button is pressed, the differential gear moves one tooth via a lever. As a result, the hour hand and city disc advance by one hour and one time zone, and the date also advances after midnight. However, if the city disc rotates further and crosses the International Date Line, the lever connected to the city disc pushes the differential gear in the opposite direction, moving the date display hand back one day. In all other situations, the force moving one tooth cancels out the force moving it back one tooth, and the date display hand does not move.
Incidentally, when creating the World Time in 2000, Barra's biggest challenge was avoiding the double jump of the city disc. Indeed, it is extremely difficult to move a heavy city disc instantaneously and stop it precisely. "Development was extremely difficult, and the commercial release was delayed by a year, but as a result, Patek Philippe's World Time became extremely reliable," he explains. So, what about the new World Time with the added date mechanism? Moreover, as the diagram shows, the differential gear that drives the date display is quite compact. When asked about the durability of the differential gear, Barra replied, "There are absolutely no problems."
With the addition of the date display, and the differential gear that controls it, wouldn't the push button become heavier? "The force required to press the push button is about 9N (approximately 0.92Kgf). The on/off function causes the three displays (hour hand, 24-hour disc, and city disc) operated by the control lever to jump simultaneously, but the force is the same as for other world time watches. However, between Auckland and Midway, which cross the International Date Line, the force required increases to about 14N (approximately 1.43Kgf)." Incidentally, the calendar movement with a large date developed by Patek Philippe for the "CUBITUS" is instantaneous. Considering that the force required to operate this is 2Kgf (approximately 19.6N), the push button on the world time watch is surprisingly light.
Another challenge pointed out by Philippe Barra was the hands. To improve legibility, Patek Philippe chose glass, rather than brass or gold, for the pointer date hands. Sapphire crystal would seem more suitable if it were a transparent material, but they settled on ordinary glass because they couldn't properly polish the sides of the hands. Barra also stated that "assembly and painting are difficult." Indeed, unlike brass, gold, or steel, glass has no flexibility. If it were simply press-fitted, the base of the hand would likely break. On the other hand, if it were attached loosely, it wouldn't be able to withstand the shock when the date changes. We don't know how they solved it, but there must be some know-how unique to Patek Philippe.
From a cynical perspective, the new World Time watch with added date display could be seen as a move to keep competitors in check. The patent for the World Time watch, announced in 2000, expires in 25. This means other companies will likely release their own user-friendly World Time watches in the style of Patek Philippe. In that case, adding a date display to further differentiate the product is a wise move. Whatever the reason, the fact that it's a truly functional watch is typical of Patek Philippe today. The new World Time watch is worth owning if you have the financial means. It's user-friendly, has excellent operability, and boasts outstanding accuracy.
