Millennial marvel
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Millennial marvel

IWC's Portugieser Eternal Calendar needs no adjustment until the year 3999

Millennial marvel
An additional mechanism recognises the leap year exceptions.

Swiss watchmaker IWC Schaffhausen launches its first secular perpetual calendar in the leap year of 2024. An engineering feat, the Portugieser Eternal Calendar automatically takes into account the Gregorian calendar's leap year exception rules.

Moreover, a record-breaking moon phase display takes a marvellous leap with a mathematical accuracy of 45 million years compared to 577.5 years provided by the complication installed in the first Portugieser Perpetual Calendar from 2003.

Stepping back in time, the International Watch Company was born in the leap year of 1868.

In 1582, Pope Gregory XIII introduced his dating system, which has now been adopted by most countries around the world. In October 1582, the pope wiped out 10 days to implement the Gregorian calendar. While the Julian counterpart added a leap day every four years, his refined calculation of the leap years kept the calendar more in sync with the actual solar year.

Only centurial years evenly divisible by 400 count as intercalary years with the extra Feb 29. Hence, 2000 and 2400 are leap years while 2100, 2200 and 2300 are common years with 365 days.

Because the perpetual calendar tracks the four-year cycle of three common years followed by a leap year, it will misinterpret 2100, 2200 and 2300 as leap years and three corrections will be required over a period of 400 years.

IWC Portugieser Eternal Calendar.

IWC builds on its expertise in mechanical calendars to develop its secular perpetual calendar, which requires no adjustments as it is programmed to precisely calculate the leap years until at least 3999.

Its engineers made this possible by devising the 400-years gear to reflect the leap year exceptions of the Gregorian calendar.

The additional mechanism for the Portugieser Eternal Calendar completes only one revolution every four centuries. Meanwhile, its three indentations cause the calendar to skip the three centurial years, firstly 2100, over that period.

The sophisticated yet user-friendly timepiece is based on the same modular and synchronised design as IWC's perpetual calendars, whose displays can be advanced via a single crown.

In a 44.4mm platinum case, the eternal calendar imaginatively carries the DNA of the Portugieser, created in the late 1930s, to a faraway future.

IWC-manufactured 52640 calibre.

The new moon phase display will only deviate from the Moon's orbit by one day after 45 million years, thanks to an inventive reduction gear.

A cycle from New Moon to New Moon -- one lunation -- takes 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 the lunar cycle. A special computer program simulated more than 22 trillion different combinations of the quantity of wheels, their proportions and the number of teeth.

The chosen reduction gear train with three intermediate wheels renders the unprecedented precision of the Double Moon display. Another challenge was integrating it into the confined space of the eternal calendar module.

At 12 o'clock on the dial, the Double Moon shows the celestial body as seen from the Northern and Southern hemispheres with the negative representation giving an impression that two small moons are waxing or waning.

The lunar display consists of two super-imposed discs -- the glass disc with two small circular openings rotates above the immobile titanium disc decorated with a guilloché pattern and two blue dots.

The year appears in an aperture positioned between 7 and 8 o'clock. The date plus power reserve, month and day of the week along with small seconds are respectively indicated at 3, 6 and 9 o'clock on the intricately-crafted glass dial with a frosted and white lacquered underside.

Infusing a sense of airiness, the transparency is enhanced by the double box-glass sapphire crystals, with the one on the back revealing the newly-developed IWC-manufactured 52640 calibre with a power reserve of seven days.

Besides the mechanical masterpiece, four versions of a new perpetual calendar further illustrate the "A Tribute To Eternity" theme for the 2024 Portugieser collection.

An IWC engineer with the brand's first secular perpetual calendar.

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