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IWC’s Portugieser Eternal Calendar finally finds a solution to the perpetual calendar

Throughout history, humankind has always sought to keep time. It began with curious glances at the sun, moon and stars in the sky which turned into observations of the lunar and solar cycles. Then, as the broader notion of time was quantified into calendars, they looked at more minuscule values, breaking down and counting hours, minutes, seconds, and fractions of seconds. Today we have come to a point in civilization where timekeeping is so commonplace that we take it for granted. The people who once watched the shadows of the sundial in excitement as the hours passed have been replaced by us, who lazily glance at a digital screen to get the time. So advanced, in fact, is our civilisation that now, we have the luxury of investing instead in traditional technology for the sake of preserving culture.

The perpetual calendar within a mechanical wristwatch is a beacon of such luxury. Even though we have mastered the tracking of the Gregorian calendar with digital means, there are watchmakers who have continued picking at the gear trains of movements in the hopes of making a perpetual calendar that is truly perpetual. And it seems that those watchmakers reside in IWC Schaffhausen. This is a story about the Eternal Calendar, a secular perpetual calendar mechanism that has finally solved the peculiarities of the Gregorian calendar, theoretically being able to keep the date for ‘eternity’ and also promises to keep an accurate record of the moon phases for the next 45 million years.

LEAP OF FAITH

To understand why this problem exists in the first place, one need only look to the stars for answers. The simple explanation of a ‘year’ as most people on the planet recognise, is defined as the time it takes for the earth to make one full rotation around the sun. It is taught in schools as 365.25 days, and this is also why, in the Gregorian calendar system, every four years these quarters are added together to form an extra day on February 29. This is the leap day added every four years to what is known as a leap year, and this is the problem the perpetual calendar has already solved.

However, scientifically speaking, the exact time that the earth takes to rotate around the sun is not exactly 365.25 days but rather 365.2422 days. And if the leap years are consistently added every four years, it would progressively shift the calendar out of sync as the centuries go by. When Pope Gregory XIII instituted the Gregorian calendar system in 1582 it included the leap year exception rule where three leap years every 400 years are removed to accommodate this difference.

This leap year exception rule, where every year divisible by 100 is not a leap year unless it is divisible by 400, is the one that perpetual calendar mechanisms still can’t solve. Thus, despite what the name of the complication suggests, the calendar will still have to be adjusted in 2100, the next instance where the leap year exception rule takes place.

In the same vein, most moonphase functions are also designed with the general rule that a lunar cycle is 29.5 days. In reality, this number is again an approximation of the observed time of 29 days, 12 hours, 44 minutes, and 2.88 seconds. Therefore, with the simplest moon phase indicators working on the 29.5-day cycle, they will start to be inaccurate after a few years of functioning.

This is where IWC steps in. With their new Portugieser Eternal Calendar, they claim to have solved the problem by offering what they are calling a secular perpetual calendar complication that can not only keep track of the leap years but also observe the leap year exception rule resulting in a timekeeping mechanism that will theoretically display the correct date in perpetuity. And their moonphase indicator? They haven’t yet found a perfect solution, but are flexing hard with a mechanism that, they say, will be accurate for the next 45 million years. When the Eternal Calendar was launched, IWC cheekily stated that we would just have to take their word on this but since then, the Double Moon indicator on the watch has been recognised by Guinness World Records as the “most precise lunar phase wristwatch” with a theoretical deviation of just one day in 45,361,055 years.

COMMON DENOMINATOR

Solving this problem digitally is easy as most computers understand fractions and decimal places. And with the proper input instruction, you can get a computer to adhere to any nonconflicting rule like leap years and leap year exceptions. But when it comes to mechanical watchmaking, it is a lot more complex. Instructions have to be relayed in gears, springs and cams, while there is also the constraint of space in a wristwatch. This is why we mentioned at the top of the article that civilisation has to be at a place where excess is possible to devote the resources that luxury companies have to finding a more ‘artistic’ solution to a problem that has already been solved, vis-à-vis the calendar.

Kurt Klaus who celebrates his 90th birthday this year

However, in order to arrive at the Eternal Calendar, IWC had to have some considerable technical expertise in the complication. Their experience with perpetual calendars dates back to the 1980s with Kurt Klaus who incidentally is celebrating his 90th birthday this year. Klaus, was the student of yet another famous name at IWC, Albert Pellaton, of the Pellaton winding movement that is still in use today.

The IWC Da Vinci Perpetual Calendar Ref. 3750 in light yellow gold

In 1985 he pioneered an ingenious new perpetual Calendar movement within the Da Vinci Perpetual Calendar Ref. 3750 which allowed the user for the first time to set all the displays by simply turning the crown. And the genius of this perpetual calendar movement was that he achieved this through 82 individual components. Additionally, he also created a new moonphase indicator that was precise up to 122 years. Klaus’ perpetual calendar movement was also the first to offer a digital year display that could showcase the year until 2499. An interesting fact that IWC states is that that the 100-year numeral of this year display will advance only a mere 1.2mm in a century but a point on the balance wheel would have travelled a distance equivalent to 40 orbits of the Earth in the same time.

This was hardly the start of IWC’s foray into the perpetual calendar complication but it was a significant milestone in terms of the modern watchmaking landscape. The 1980s was the time of quartz technology and it took real gumption and perhaps foresight, both on the part of Klaus and IWC to choose to develop a mechanical calendar complication.

This choice, arguably has bore abundant fruits throughout the years as the perpetual calendar with moonphase indicator exists in some shape or form in the major IWC collections including the Pilot, Portofino and of course the Portugieser. And it has gotten upgrades over the years. In 2003 the perpetual calendar debuted within the Portugieser collection and its moonphase indicator gained accuracy, from needing adjustments once every 122 years to once every 577.5 years.

AGE OF ETERNITY

To say that IWC is excited about the Portugieser Eternal Calendar may be the understatement of the year as it was launched practically the moment the first pieces were fully assembled. Earlier this year at Watches & Wonders Geneva there were literally only two pieces of this watch circulating within their booth. Two pieces to serve thousands of journalists and more than ten thousand retailers, all clamouring to see this marvel that solved what the perpetual calendar complication couldn’t.

So how did they do this? The simple answer is to increase the duration of its calendar cycle. If you think about your average date display or the complete calendar complication it is simple because it is programmed to a 1-month cycle. This means that every month regardless if it’s a 30-, 28- (or 29) or 31-day month the date will always go to the 31st requiring an adjustment 5 times a year for the shorter months. The next step up in complexity is the Annual calendar which was designed in a 12-month cycle for the mechanism to understand the difference between the longer and shorter months.

Then comes the perpetual calendar. For it to understand that every four years a leap day has to be added to the end of February during a leap year it has to be designed to function in a four-year or 48-month cycle. With the same logic, the engineers at IWC solved the problem of the leap year exception rule by extending the programme cycle of the Eternal Calendar to a 400- year or 4,800-month cycle. This means, that inside the newly developed IWC-manufactured 52640 calibre movement, there is a gear that will only make one full rotation in four centuries. This gear contains three indentations which causes the perpetual calendar to skip three leap years over that period which happens next in 2100, 2200 and 2300.

Of course, if you’re going to have a secular perpetual calendar mechanism that theoretically keeps the date for ‘eternity’ the moonphase indicator that is accurate to 122 or 577.5 years simply won’t do. To solve this problem, IWC installed a reduction gear between the base movement and the moon phases disc to get as close as possible to the actual duration of the lunation – the aforementioned 29 days, 12 hours, 44 minutes, and 2.88 seconds. The design of this reduction gear, now this is the interesting bit, was done by engineers using a special computer programme to simulate more than 22 trillion different combinations before settling on this mechanism that they say will be accurate for the next 45 million years.

What is perhaps overshadowed by the 45 million years and the Eternal part of the watch is the details they have afforded on the dial of this Portugieser. They chose to go with a glass dial which is frosted and lacquered on the underside. On top, there are clear subdials and the numerals and characteristic Portugieser minute scale are printed on a white lacquered flange sitting between the glass dial and the front glass. The whole thing gives the watch a sort of dimensionality, revealing only a very inconspicuous clue that when 2100 rolls around, finally, no adjustments will have to be made.

THE END

Theoretically, if the Gregorian calendar system doesn’t change, the Portugieser Eternal Calendar presents a perfect calendar complication that would never run out of sync. However, at present IWC claims the secular perpetual calendar complication will be accurate until at least 3999 because it has not been officially decided if the year 4000 will be a leap year or not.

Assuming the rules stay status quo and, of course, humanity continues to exist, what then is eternity? How long will the calendar of the Eternal Calendar be accurate? These types of questions are too complex for us and perhaps even IWC to answer. So, they sought out, Brian Cox, particle physicist and professor at the University of Manchester, to help out:

“In our current baseline model of the universe, we understand that the universe is not only expanding, but it is expanding at an accelerating rate. If the universe continues to do that, we will reach a point when everything is so far apart from everything else, and the temperature of everything is the same. Technically, we would say that entropy always increases as the universe goes from a highly ordered state to something messier. However, one of the things that we know about a clock is that it is a thermodynamic device. To build a clock, you need a temperature difference. In the far future, we will reach a point when no more temperature differences exist in our universe. I suppose that, then, time will have gone. When we get to the point where nothing happens in our universe – when there are no more temperature differences, and you can’t even build a clock. That, to me, is eternity. It goes on forever, and time will have ceased to have meaning. To give you a rough number: we currently believe that the supermassive black hole in the centre of our galaxy will evaporate in something like 10 to the power of 100 years. That’s one with 100 zeros. So, we are talking about an unbelievable amount of time before that probably will happen.”

So in short, a really freaking long time.

Leaps And Bounds: The Alluring Green Dial of Blancpain’s Villeret Quantième Perpétuel Ref. 6656

How often do you think about a leap year? The seemingly innocuous phenomenon that happens once every four years, adding a single day to February. For most of the world’s population it is probably just “oh, there is a February 29th this year” as they see the date on the screen of a smartphone, smartwatch or Google calendar. But, for us watch enthusiasts, on the other hand, February 29th is the day when we finally get to see the perpetual calendar complication go to work. The day when your mechanically driven timepiece can intuitively understand that in 2024, February doesn’t end on the 28th and therefore can automatically compensate for the extra day, and subsequently the arrival of March.

Put to a non-watch person, it may seem that all the research and development and investment from the brand side, along with the hefty asking price of a perpetual calendar, to see it in action once every 1,460 days is probably not justified. However, this is the reason you buy a perpetual calendar. Not an annual calendar or a complete calendar, which is comparatively much cheaper. You buy a perpetual calendar so you can set it once, and if continuously powered, will keep the date until 2100 whereby many of us reading this would no longer be alive.

In honour of the year that will see the Perpetual Calendar complication put to good use, for our Spring 2024 issue, we take a closer look at this complication from Blancpain. More specifically the Villeret Quantième Perpétuel Ref. 6656, a model that represents the confluence between the trifecta of complexity, functionality and design. This model from the manufacture is not new per se but for 2024 it has, for the first time, been given a deep green dial inspired by the fir forests of the Vallée de Joux and paired with an elegant red gold case, giving us the perfect opportunity to revisit the perpetual calendar complication, a complicated that many collectors would probably have on their grail list.

THE DIFFERENCE A DAY MAKES

To understand what makes a perpetual calendar so special, one must first go back to the basics of the date function. At its most basic level, the date mechanism simply follows the advance of the hour hand. For every 24 hours that pass, the date wheel is advanced one day forward. If all months had 31 days this complication wouldn’t have a problem because mechanics thrive on repetition (I recommend playing the video game Opus Magnum to better understand what I mean). However, as we know, some months have 30 days while others have 31. If this was the only variable in a calendar, then, still a perpetual calendar wouldn’t be too difficult to make as the mechanism only has to compensate for two variable factors. Adding on yet another layer of complexity is the fact that February has 28 days which makes this month out of the 12 yet another anomaly which has to be mechanically adjusted.

For each layer of ‘rule’ added to a calendar the mechanics inside have to increase exponentially in terms of complexity to comply. For example, the traditional date complication is simple to manufacture because it follows one rule, and the human (wearer) will manually compensate for the discrepancies between the different days of the month. This means that the date wheel will just automatically advance to 31 every month and five times a year this must be manually corrected.

The next layer of complexity is a movement that can discern between the months that have 30 and 31 days and automatically advance the date as such. This is the function of an annual calendar complication. To achieve this, engineers devised a special cam that takes into consideration the pattern of days in the month within a 1-year cycle. But, as the name alludes, the Annual calendar still requires one manual adjustment to the date every year which is in February, regardless of whether it is a leap year. Interestingly enough, even though the perpetual calendar was invented by Thomas Mudge around the 1760s it was only in 1996 that the simpler annual calendar was invented.

For a perpetual calendar to work, the mechanism within the movement has to be capable of not just ‘understanding’ the patterns of 30 and 31 days within a year, it also has to ‘remember’ that February has only 28 days. And the most important of which, is it has to keep track that every four years, during a leap year, there is an extra day on February 29th. Explaining the mechanism to achieve this would probably take more pages than we have for this article so for the sake of brevity, the ‘memory’ of a perpetual calendar can be boiled down to a cleverly designed cam that records the length of months in a four-year cycle. For this Ref. 6656 specifically, the cam is based on an 8-year cycle recording two consecutive leap years, which can clearly be observed on the subdial at 12 o’clock. On paper, it may seem simple enough to add one day to February every four years, but in reality, the Perpetual calendar is even more complicated than the fan-favourite tourbillon and is probably closer in number of parts to a minute repeater.

Within this new version of the Villeret Quantième Perpétuel Ref. 6656, beats the calibre 5954 automatic movement with its integrated perpetual calendar complication. It is capable of offering a power reserve of 72 hours when fully wound and offers the same anti-magnetic properties thanks to its silicon hairspring.

Even though the word perpetual suggests that the watch need not ever be adjusted, Blancpain’s perpetual calendar, and for that matter almost all perpetual calendar complications are not perfect because they still must be manually adjusted in 2100. If you take the rule that a leap year happens every year divisible by four, then technically 2100 should be a leap year. But it’s not. This is because the exact time that Earth makes a full rotation around the sun is not exactly 365.25 days but rather 365.2422 days. By this logic, if we continue to apply the leap year rule, after a couple of hundred cycles, our seasons will start to get out of sync. Therefore, when the Gregorian calendar (the one we use today) was invented it stated that century years would have to be divisible by 400 for it to be a leap year. Thus 2100, 2200 and so on, will not be leap years to compensate.

BETTER SAFE THAN SORRY

On the subject of manual corrections, the perpetual calendar complication can be notorious when it comes to its adjustments. In perpetual calendars of the past, it has been said that manipulating and adjusting the watch at certain times could easily damage the watch earning it a round trip home to Switzerland and along with it, a large bill for the repairs. And this forbidden period was between the few hours before midnight and the few hours that followed. During this time, the calendar indications are changing, and any manual correction applied could easily damage the delicate gears.

With the Villeret Quantième Perpétuel Ref. 6656 from Blancpain, this is no longer an issue as the watch designers at the manufacture have managed to eliminate this risk entirely. When the user tries to make the adjustment while changes are happening, a clutch disengages the system to prevent any damages from occurring. But the ability to do this doesn’t come without its cost, and according to Blancpain, they needed 40 per cent more components compared to a traditional complication to achieve this. Of course, all of this is hidden beneath the dial so all the wearer sees, is a clean and elegant design on its top side.

Another testament to the usability of Blancpain’s perpetual calendar movements is the fact that since 2005 they have introduced a patented system of manual adjustment – under-lug correctors. Traditionally these manual adjustment mechanisms have always been built into the sides of the cases. In fact, most other perpetual calendars still use these correctors, which appear as small dimples on the case of the watches. The clever use of under-lug correctors by Blancpain enhances the watch in two ways.

The first of which is purely functional where instead of needing a tool to depress the dimples on the case, the lever on the underside of the lugs can be manipulated using one’s fingernails. Secondly, the discarding of these dimples can now allow the watch case to have an entirely smooth surface, adding heaps to the elegance of the watch. This is especially prominent in the case of the Reference 6656 where the beautifully minimalistic dial is complemented by the blemish-free red gold polished case.

MOON FACE INDICATOR

Okay, before you grab your pitchforks protesting this sub-heading, it is indeed quite a literal reference to the little face present on the moonphase indicator on the dial. The moonphase has always been a significant part of Blancpain’s history; One could even say that it is the perfect representation of Blancpain’s ethos as a watch company.

As the story goes, the legendary Jean-Claude Biver said when he bought Blancpain in 1982: “There has never been a quartz Blancpain, and there never will be.” Back then, even the Swiss watch brands were starting to dabble with quartz technology during the era of the quartz crisis. But Blancpain took an opposite stance, instead, doubling down its efforts to cement the mechanical watch’s place in contemporary times by demonstrating how quartz could never replicate the complexity, craftsmanship and history of traditional watchmaking. One of the first complications they decided to make in its modern era was a moon phase indicator in 1983.

Looking at the moon phase indicator on the new Villeret Quantième Perpétuel Ref. 6656, I feel like the face on this moon is portraying something akin to an all-knowing smirk. Perhaps it knows that Blancpain’s choice to make a statement with this complication basically predicted the role of the mechanical watch for contemporary times, not just for Blancpain, but arguably for the entire luxury watch industry that exists today.

The design of the dial is the same Ref. 6656 that was first launched in 2018 which also served as a replacement for the Ref. 6057 which offered a similar design, day, date, month and leap year indicators in three subdials, but in a smaller 38mm case. The new Ref 6656 on the other hand is housed in a 40mm red gold case complete with the collection’s signature double-stepped case. Last but certainly not least, the new look is also defined by the mesmerising, deep green of the dial. The colour along with its sunburst pattern was inspired by the fir forests of the Vallée de Joux that surround the Grandes Complications workshop where the watch is meticulously crafted by its master watchmakers.

A Closer Look at the History of Patek Philippe’s Perpetual Calendar Timepieces

In May 1902, an object uncovered by archaeologists cast some light on mankind’s historical grasp of horology and our ability to use algorithms to compute the day of the week for any given year, month, and day of month. What we take for granted today on our wrists, was a mechanical marvel and feat of ingenuity for the makers of what came to be known as the Antikythera device.

The ancient Greek ‘computer’ was able to predict the motion of celestial bodies and eclipses for calendar and astrological purposes. Make no mistake, it was a computer; what we do today with silicon wafers and microchips was computed with gears like those of a clock and uniquely shaped components with teeth reminiscent of Radian-scale protractors, likely used to translate mechanical instructions for the “operating system”.

To early 20th century eyes, the purpose of the device was obscure – nothing at this level of technology had been discovered in antiquity. As we approached the 21st century, the advent of advanced imaging technology revealed that intricate gear trains within the device operated at least six indicators displaying all manner of celestial time: the sun, the moon and the four closest planets which men of the era could perceive: Mercury, Venus, Mars, Jupiter and Saturn. And we haven’t even discussed the three dimensional moonphases and the twin dial system that displayed the calendar information, and the stars that ‘rose’ and ‘set’ on any given date.

Believed to have been designed and constructed by Greek scientists as far back as 205 BC, the Antikythera (named for the island coast where the object was discovered) was possessed of technological and engineering features lost to Europe until the development of the first mechanical astronomical clocks in the 14th century.

As it was then and as it is now, these analogue computers essentially take complex tables and calculations and render them arithmetically into gears, wheels and other innovative horological components (like snail cams for leap years). Perpetual calendars we know today from the aforementioned 14th century mechanical clocks, thus, while the underlying principles of ancient analogue computers and mechanical clockwork may be similar, their developmental paths are entirely different.

That said, the devices in question are able to reckon the days, months and years in figurative perpetuity (most perpetual calendars are accurate to a hundred years before requiring adjustment), hence the name perpetual calendar.

While Patek Philippe can lay claim to creation of the first perpetual calendar wristwatch, it was an English watchmaker named Thomas Mudge who invented it in the 18th century. The 1762 Mudge perpetual calendar pocket watch tracked and indicated different measures of time such as day, month (lunar month) and length of year.

The ingenuity of men such as Mudge and the watchmakers at Patek Philippe allowed them to devise minute gears and springs to compute relatively complex arithmetic into an easily understood display. Patek Philippe’s first serially produced perpetual calendar wristwatch spanned 34mm and featured an instantaneous retrograde date display, day and month indications, and a moon phase indicator. Though the Geneva manufacture would sell its first perpetual calendar wristwatch to an American collector named Thomas Emery in 1927, they would only begin serial production of hand-wound perpetual calendar wristwatches 14 years later, beginning with the famed ref. 1526.

By 1962, we would see the first hand-wound perpetual calendar references, predecessors of the contemporary self-winding perpetual calendar wristwatches. This new age was heralded with the ref. 3448 and has since been perpetuated (pun intended) by the legacy of contemporary Patek Philippe Perpetual Calendar references.

(To be clear, other watchmaking companies also got in on the action, but there is a kind of transcendent magic to Patek Philippe perpetual calendars that we are following here – Ed.)

The first wristwatch with perpetual calendar

Why is adjustment needed every 100 years?

Mudge invented the mechanism only 10 years after the Gregorian calendar was officially adopted in England, his home. His mechanical perpetual calendar interprets the Gregorian calendar and its 400 year cycle comprised of 303 common years and 97 leap years totalling 146, 097 days into an engineered series of analogue components and wheels. Each of these moves in concert to display the precise day, date and month (even their varying lengths) without additional adjustments even for leap years. Why then do our contemporary perpetual calendars still need adjustment after a 100-year period? Then as now, a cycle is a 100-year period with 25 leap years and in some instances, a 100-year period with 24 leap years but at its core, all calendars begin with three essential movements of Earth (and its satellite, the moon) – our axial rotation, with which we calculate hours in a day; orbit of the moon, with which we calculate month and finally; how long it takes for the Earth to orbit the Sun, 364.25 days or one year.

Did you know that the “simpler” Annual Calendar (invented by Patek Philippe) actually has more parts as well?

An annual calendar has about 40 more parts than a perpetual calendar due to the fact it is using a system of gear trains compared with the perpetual calendar’s system of levers.

So an annual calendar has more parts but ironically, is more accessible than a perpetual calendar as the gear train construction is still simpler to assemble and fine-tune than the levers of the high complication. One of the main complexities of perpetual calendar is in adjusting that one big lever that activates simultaneously various parts of the movement.

From: World of Watches #39.