One of the most impressive and horologically advanced timepieces presented at Watches & Wonders 2024 is the new IWC Portugieser Eternal Calendar. IWC now pushes the boundaries once again with its first secular perpetual calendar. In addition to recognizing the different lengths of the months and adding a leap day every four years, the Portugieser Eternal Calendar also takes into account the Gregorian calendar’s complex leap-year exception rules. A newly engineered 400-year gear ensures that the calendar automatically skips three leap years over four centuries —an event that will occur for the first time in the year 2100. The watch is accurate until the year 3999.
Another key feature of this watch is the extremely precise moon phase display. Thanks to a newly developed reduction gear, the Double Moon phase display will only deviate from the moon’s orbit by one day after 45 million years. The Portugieser Eternal Calendar features an intricately finished platinum case measuring 44.4 mm in diameter, a sapphire crystal dial, and double box-glass sapphire crystals in the front and the back, and is delivered on a black alligator leather strap from Santoni.
Translating the irregular calendar into a mechanical program for a wristwatch remains one of the most challenging engineering feats in fine watchmaking. The Gregorian calendar, which is used across most continents and cultures today, divides the year into twelve months with 28, 30, or 31 days. Years that are divisible by four count as leap years, meaning that a 29th day must be added at the end of February. However, an additional correction is needed to keep the calendar in sync with the actual solar year: only those centurial years that can be divided by 400 are leap years, and all others are common years. This means that 2000 and 2400 are leap years, while 2100, 2200, and 2300, for example, are common years. A traditional perpetual calendar; however, is only programmed for a four-year cycle, in which three common years are always followed by a leap year. By design, it will interpret the year 2100 as a leap year and need a correction. The same will happen again in 2200 and 2300. As a result, a perpetual calendar will need three corrections over 400 years. A secular perpetual calendar like the new IWC Portugieser Eternal Calendar ref. IW505701, on the other hand, is mechanically programmed to take these complex nuances into account. It will calculate the leap year correctly until at least the year 3999, as it has not yet been officially decided whether the year 4000 will be a leap year or not.
Things to Know About the Watch
The Portugieser Eternal Calendar is based on the same modular and synchronized design as the existing perpetual calendar. All its displays can be advanced using the crown. However, while the perpetual calendar is programmed for a four-year cycle, the Portugieser Eternal Calendar features an additional mechanism. Every four years at the end of February, a new module informs the calendar about whether the leap year takes place or not. This so-called 400-year gear completes only one revolution every four centuries. It contains three indentations, which cause the calendar to skip three leap years over that period. This module is designed with impressive efficiency and technical elegance and consists of only eight parts, underscoring IWC Schaffhausen’s engineering approach to fine watchmaking.
“Since Kurt Klaus developed his legendary perpetual calendar in the 1980s, IWC Schaffhausen has accumulated unique expertise in mechanical calendars that are ingeniously efficient in their design and easy to use. With the new Portugieser Eternal Calendar, we now venture further than ever before, touching the limits of eternity. Our first secular perpetual calendar automatically takes into account the Gregorian calendar’s complex leap-year exception rules by skipping the leap year three times over 400 years. True to the spirit of engineers who are always pushing the boundaries, we have also fitted this technical marvel with a moon phase display that will only deviate from the moon’s orbit by one day after 45 million years. "Chris Grainger-Herr, CEO of IWC Schaffhausen
IWC’s engineers have now used a special computer program to simulate more than 22 trillion different combinations. For the Portugieser Eternal Calendar, they came up with a new reduction gear train using three intermediate wheels. Mathematically, the display will only deviate from the moon’s orbit by one day after 45 million years. Another challenge consisted of integrating this new gear train into the confined space of the eternal calendar module. Therefore, the moon phase is displayed on the dial using the characteristic Double Moon indication, which shows the moon as seen from the Northern and Southern hemispheres. The display consists of two super-imposed discs. A celestial disc with two small circular openings rotates above an immobile lower disc with two dots. This negative representation gives the impression that two small moons are waxing or waning. Here, the lower disc is made of titanium and decorated with a Guilloché pattern. The upper disc is made of glass.
The Movement
Turning the watch over reveals the newly developed IWC-manufactured calibre 52640. This automatic movement with a bidirectional Pellaton pawl-winding system with two barrels provides a power reserve of seven days when fully wound. Parts of the winding system that are subject to extremely high stresses are manufactured using virtually wear-free zirconium oxide ceramic, and the movement has been elaborately finished with circular graining and Geneva stripes and can be admired through the box-shaped sapphire glass case back. The watch is water resistant to 50 meters.
On the Wrist & Price
On the wrist, the new IWC Portugieser Eternal Calendar wears true to its size and quite comfortably. IWC watches are renowned for their impeccable craftsmanship and timeless design, which is also evident in how they feel when worn on the wrist. Whether you opt for a robust Pilot's watch or a sleek dress timepiece like this one from the Portugieser line, wearing an IWC watch is a true delight that seamlessly combines elegance with superior wearing comfort.
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