IWC Schaffhausen – PORTUGIESER Eternal Calendar Double Moon™ Platinum 44.4 mm Automatic 2024
Schaffhausen/Geneva, 2024: IWC Schaffhausen introduces the Portugieser Eternal Calendar at Watches and Wonders Geneva. Drawing on the extensive calendar expertise it has acquired since introducing the perpetual calendar almost four decades ago, IWC now pushes the boundaries once again with its first secular perpetual calendar.
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In addition to recognising 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-years gear ensures that the calendar automatically skips three leap years over four centuries – an event which will occur for the first time in the year 2100. Another key feature of this watch is the extremely precise moon phase display. Click, to see the large size. ▶ BIG FOTO .jpg)
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 and a black alligator leather strap from Santoni. The extensive use of glass elements such as a glass dial and double box-glass sapphire crystals showcases the ingenious mechanism inside. The increased transparency also creates a unique sense of lightness, airiness and understated elegance.Click, to see the large size. ▶ BIG FOTO 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, all others are common years. This means that 2000 and 2400 are leap years, while 2100, 2200 and 2300, for example, are common years.
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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 a period of
400 years. A secular perpetual calendar like the
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.
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“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
THE 400-YEARS GEAR SKIPS THREE LEAP YEARS IN FOUR CENTURIES
The Portugieser Eternal Calendar is based on the same modular and synchronised 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.
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This so-called
400-years 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.
MOON PHASE WITH A CALCULATED ACCURACY OF 45 MILLION YEARS
Since the introduction of the perpetual calendar almost four decades ago, IWC has also taken great strides to continuously improve the accuracy of its moon phase displays.
Click, to see the large size. ▶ BIG FOTO 
While the
Da Vinci Perpetual Calendar Chronograph (
Ref. IW3750) from
1985 featured a moon phase precision of
122 years, the first
Portugieser Perpetual Calendar (
Ref. IW5021) from
2003 impressed with a moon phase accuracy of
577.5 years.
IWC’s engineers have now taken on the challenge to develop a new moon phase display with unprecedented precision.
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The difficulty in displaying the moon phase on the dial of a watch lies in the fact that the moon does not follow a daily rhythm in its orbit around the Earth. A cycle from new moon to new moon – one lunation – does not last 30 days, but rather 29 days, 12 hours, 44 minutes, and 2.88 seconds. The duration of one calendar month must therefore be reduced as close as possible to one lunar cycle. This is achieved by placing a reduction gear between the base movement and the moon phase disc.
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The key to high precision lies in the quantity of wheels used, their proportions and the number of teeth they have. IWC’s engineers have now used a special computer program to simulate more than 22 trillion different combinations.
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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 in integrating this new gear train into the confined space of the eternal calendar module.
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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.
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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.
INTRICATELY CRAFTED GLASS DIAL AND DOUBLE BOX-GLASS
The Portugieser Eternal Calendar features an intricately finished platinum case with polished and brushed surfaces. Another highlight is the glass dial, which is manufactured in a complex process. In the first step, the underside of the dial is frosted and lacquered in white.
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The subdials are machined and polished separately and subsequently fixed onto the dial. In the next step, the printing is applied, and the appliques are mounted by hand. The depth of the glass lends the print and appliques a floaty lightness. The numerals and the characteristic
Portugieser minute scale are printed on a white lacquered flange sitting between the glass dial and the front glass.
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The box-glass sapphire crystals are machined and polished in an elaborate process.
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The
Portugieser Eternal Calendar is fitted with a black alligator leather strap from the Italian leather artisan Santoni with a platinum folding clasp.
IWC-MANUFACTURED 52640 CALIBRE
WITH SEVEN DAY POWER RESERVE
At work inside the platinum case is the newly developed IWC-manufactured 52640 calibre. The high-end calibre features a highly efficient Pellaton winding system. Using movements of the rotor in both directions, it reliably builds up a power reserve of seven days (168 hours) in the two barrels.
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Parts of the winding system that are subject to extremely high stresses are manufactured using virtually wear-free zirconium oxide ceramic. 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 WORLD’S MOST PRECISE LUNAR PHASE WRISTWATCH: THE IWC SCHAFFHAUSEN PORTUGIESER ETERNAL CALENDAR NOW HOLDS THE GUINNESS WORLD RECORDS™ TITLE
Schaffhausen/London, 26th June 2024: The newly introduced Portugieser Eternal Calendar has been officially recognised by Guinness World Records as the “most precise lunar phase wristwatch”.
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With a theoretical deviation of just one day in 45,361,055 years, the Double Moon™ indication of the Portugieser Eternal Calendar beats the previous world record by more than 43 million years. This is made possible by a new reduction gear train with three intermediate wheels, which reduces the duration of one calendar month as precisely as possible to the duration of one complete lunar cycle.Click, to see the large size. ▶ BIG FOTO .jpg)
The moon phase display is arguably the most charming complication in watchmaking. It displays the current phase of the moon on the dial, ensuring that no full moon is missed – even if it is obscured by clouds. Since the introduction of its perpetual calendar almost four decades ago, IWC Schaffhausen has taken great strides to continuously improve the accuracy of its moon phase displays.
Click, to see the large size. ▶ BIG FOTO 
Developed by
IWC Schaffhausen’s former head watchmaker
Kurt Klaus, the first perpetual calendar debuted in
1985 with the
Da Vinci Perpetual Calendar Chronograph (Ref. IW3750) and offered a moon phase accuracy of
122 years. In
2003,
IWC introduced the
Portugieser Perpetual Calendar (Ref. 5021), featuring a moon phase display with an enhanced precision of
577.5 years.
Click, to see the large size. ▶ BIG FOTO 
The new Portugieser Eternal Calendar pushes the boundaries again: with a theoretical accuracy of more than 45 million years, it has now been officially recognised as the “world’s most precise lunar phase wristwatch” by Guinness World Records (GWR). Established in 1955, GWR has evolved to the globally most recognised authority on record-breaking achievements – verifying and documenting both human and natural records. Before being awarded its title, each record is carefully audited to comply with their strict quality standards and needs go undergo a rigorous verification process.
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The moon phase of the Portugieser Eternal Calendar exemplifies the culture of engineering and innovation we live every day at IWC. From our apprentices and trainees to our most experienced watchmakers and engineers, we are continuously pushing the boundaries of what is possible in fine watchmaking. This record is a great recognition of their hard work and our watchmaking expertise
Stefan Ihnen, Associate Director Technics of IWC Schaffhausen
DISPLAYING THE MOON PHASE PRECISELY IS A CHALLENGE
In the moon phase display, a reduction gear train is placed between the base calendar module and the moon phase disc. This gear train reduces the duration of one calendar month to the duration of one synodic month, which equals 29 days, 12 hours, 44 minutes and 2.88 seconds.
Click, to see the large size. ▶ BIG FOTO.jpg)
The accuracy of the display depends on the number of wheels used, their proportions and the number of teeth they have. For the Portugieser Eternal Calendar,
IWC’s engineers devised a new reduction gear with three intermediate wheels – two more than in the previous module with an accuracy of
577.5 years.
Click, to see the large size. ▶ BIG FOTO To develop a solution that is sufficiently robust and will function reliably for extremely long periods of time, they defined key parameters such as the minimum and maximum number of teeth per wheel. A computer simulation program created specifically for this purpose was then tasked with calculating almost 23 trillion different combinations of wheels and teeth. In an iterative process, the engineers gradually worked their way towards the perfect combination of wheels for this specific application.
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Assuming a constant duration of the synodic month of 29 days, 12 hours, 44 minutes and 2.88 seconds, the display would theoretically only deviate from the orbit of the moon by one day after
45,361,055 years.
LIGA PROCESS OFFERED THE REQUIRED PRECISION
Calculating the wheels was, however, not the end of the story. In order to achieve an even higher display accuracy, the backlash between the wheels was minimised by optimising the tooth geometry. To ensure that the tiny components function reliably over extremely long periods of time, alternative approaches also had to be adopted in manufacturing.
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As traditional metal machining would not have offered the precision needed,
IWC’s engineers opted for the so-called
LIGA process to manufacture the wheels.
LIGA involves lithography, electroplating and moulding and is often used in the semiconductor industry.
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This process permits the production of exceptionally homogenous and smooth microstructures with a degree of precision that conventional manufacturing capabilities would not even be remotely capable of.
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TECHNICAL SPECIFICATIONS
Model: PORTUGIESER Eternal Calendar Double Moon™
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Ref. IW505701 - Platinum
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FEATURES
- Mechanical movement
– Pellaton automatic winding system
– Power reserve display
– Secular perpetual calendar with displays for the date, day, month, year in four digits
– Perpetual moon phase with 45,000,000 years accuracy for both northern and southern hemispheres
– 400-years gear for the recognition of irregular leap years
– Small hacking seconds
– Rotor in 18-carat gold
– See-through sapphire glass back
MOVEMENT
IWC-manufactured calibre 52640
Frequency: 28,800 A/h | 4 Hz
Jewels: 54
Power reserve: 7 days (168 h)
195 Components
Winding: Automatic
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WATCH
Materials: Platinum
Diameter: 44.40 mm
Height: 15.00 mm
Water-resistant: 5 bar
DIALWhite
dial. Glass dial with white lacquer
Rhodium-plated hands and appliques
Day & Night indication in the shape of a globe at 9 o’clock
Glass: Sapphire, double box-glass, antireflective coating on both sides
STRAPBlack alligator leather strap by
SantoniDistance between horns:
22.0 MM
Platinum folding clasp
🔴 Public price: CHF 150'000 / 156,500 EUR / $ 160,000 💰Guide price
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Further Information
IWC Schaffhausen Baumgartenstrasse 15 · CH-8201 Schaffhausen
Phone +41 (0)52 235 75 65 · Fax +41 (0)52 235 75 01 · press@iwc.com ·
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Press releases - 2024
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IWC Schaffhausen
Baumgartenstrasse 15 ·
CH-8201 Schaffhausen
Phone +41 (0)52 235 75 65 ·
Fax +41 (0)52 235 75 01 ·
Mobile +41 (0)79 957 72 52
E-mail info@iwc.com
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