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Alongside the tourbillon and the minute repeater, the perpetual calendar ranks among the most demanding complications in mechanical watchmaking. The main reason is that the longer a calendar is meant to run without correction, the more exceptions have to be accounted for and "translated" into corresponding mechanical solutions. We take a closer look at what this involves and, for our readers, examine several perpetual calendar watches from renowned luxury watchmakers such as Breitling, Chopard and Omega.
The Perpetual Calendar Watch – A Practical Addition to Timekeeping
Normally, the division of labor between watches and calendars is clear: one shows the current time in hours, minutes and seconds, the other tells you the year, month and day. In many situations, however, it is helpful to be able to read not only the time but also the date at a glance at the dial.
For this reason, many wristwatches display the date in addition to the time, either via numerals that appear in a small aperture in the dial, or by means of a dedicated date scale around the edge of the dial or a small subdial. Since the latter requires an additional hand, this solution has come to be known as a pointer date.
A date display is relatively easy to achieve technically and is probably the most common complication today on mechanical wristwatches, as well as on quartz watches. Even so, it already reveals a central challenge that every calendar function in a mechanical watch has to overcome.
Exceptions and Irregularities Complicate the Engineering
This challenge stems from the fact that the Gregorian calendar in use today contains a number of exceptions and irregularities that make continuous mechanical display difficult. With the date, for example, the problem is that some months have thirty-one days while others have only thirty. Then there is February, which lasts 28 days in ordinary years but 29 days in leap years. In total, then, there are four different month lengths. On most watches with a date, the problem is simply solved by resetting the date by hand at the start of a new month. This also applies to so-called triple date or full calendar watches, which display the day of the week and the month in addition to the date.
It is of course more convenient and technically more elegant if, once set, the display always shows the correct date. This is possible in principle, but considerably more complex than a display that has to be corrected by hand every month. It becomes even more complicated when the day of the week and the month, and possibly also the year and the current moon phase, are to be displayed as well. If a watch can display this information for an entire calendar year without intermediate corrections and only needs to be adjusted by hand at the beginning of March, it is called an annual calendar. If the calendar display runs for an entire four-year leap-year cycle without needing correction and only has to be reset on February 29 of the leap year, it is referred to as a four-year or semi-perpetual calendar.
To display February 29 correctly as well, the movement would require an additional wheel that turns on its own axis only once every four years.
Perpetual Calendar Watches – Masterpieces of Mechanical Watchmaking
If setting the date even once every four years is too much trouble for you, you will have to opt for a perpetual calendar watch – or do without a date display altogether. In the eyes of many watch connoisseurs, perpetual calendar watches are the absolute pinnacle of mechanical watchmaking – and rightly so. To join this exclusive top tier, a watch must be able to display the date, day of the week and month correctly not just for more than one leap-year cycle, but until the year 2100 without any intermediate correction.
Because of the considerable manufacturing effort required, perpetual calendar watches belong to the very top tier not only technically but also in terms of price. This is all the more true when the complication is combined with a year display or a moon phase. A far more affordable option is an electronic solution. Two examples from Breitling and Omega illustrate that such watches are nonetheless not cheap goods but high-quality products from the luxury segment.
Breitling Cockpit B50 and Omega Speedmaster Spacemaster – Sporty Luxury Quartz Watches with a Perpetual Calendar
The electronic multifunction chronograph Breitling Cockpit B50 is an analog three-hand watch with an electronic, thermocompensated quartz movement, additionally equipped with digital displays in the form of backlit LCD screens. Designed specifically for the needs of pilots, the watch offers a chronograph function plus numerous additional aviation-related functions. These include flight time measurement, a second time zone, an electronic tachymeter, two alarms and a countdown timer. The calendar information is displayed digitally and meets the requirements of a perpetual calendar, albeit not on a mechanical basis in this case.
Omega likewise offers a watch, the Speedmaster Spacemaster Z-33, that provides further information on digital displays alongside the analog time display. In this case, these are a UTC display and two time zones, the chronograph function, a countdown timer, an alarm function – and the perpetual calendar. Visually, the model stands out for the contrast between the light titanium case and the black LCD display on the dial, against which the red-lit numerals and letters of the digital displays in turn stand out.
Chopard LUC Lunar One – A Mechanical Masterpiece with a Perpetual Calendar
Chopard presented a recent example of classic mechanical perpetual calendar watches at Baselworld 2017. For the occasion, the Chopard LUC Lunar One – flagship of the L.U.C collection – was issued in a limited special edition. The watchmakers housed the fascinating mechanics of the L.U.C 96.13-L caliber in a 43-millimeter platinum case. The deep blue sunburst dial features a big date at 12 o'clock along with three subdials in a tricompax layout. Using dedicated hands, these show the seconds, day of the week, month and leap year. The day-of-week display is also combined with a day/night indicator, while the small seconds subdial additionally shows the current moon phase together with the constellations of the Northern Hemisphere.
The particularly exclusive character of this model is reflected not least in the fact that it is one of the few watches to combine a perpetual calendar with automatic winding. Its spectacular micro-rotor is made of solid yellow gold and provides up to 65 hours of power reserve. To match the blue of the dial, the model, limited to 100 pieces, comes on a blue hand-stitched alligator leather strap with a platinum buckle. Besides the brands mentioned here as examples, a number of other renowned luxury watchmakers, including Glashütte Original and Frédérique Constant, also offer perpetual calendar watches in their collections.
If you are fascinated by mechanical solutions to the calendar problem but don't want to spend five figures, mechanical luxury watches with an annual calendar or four-year calendar are a recommended alternative.
