Watches with calendar
Watches with calendars enjoy a special position in the watch industry: complicated mechanisms with the date displayed on the dial represent one of the greatest challenges of Haute Horlogerie. A calendar, along with the tourbillon and minute repeater, is one of the 'major complications' found in watchmaking.
The Gregorian calendar as a basis
Most watches with calendars show the day, week and month and often the year, day of the week and current moon phase. This display is based on the Gregorian calendar used worldwide since the 17th century. In 1582, Pope Gregory XIII ended the Julian calendar of Julius Caesar and introduced the Gregorian calendar. The Julian year did not match the length of the solar year and with the change to the Gregorian calendar, Pope Gregory corrected this inaccuracy by eliminating the leap year every hundred years.
Full calendar, perpetual calendar and moon phase calendar
Calendar functions differ greatly among mechanical watches. There are different types of calendars: undoubtedly, the most demanding of them is the perpetual calendar which rarely has to be corrected. The reason: a caliber with a perpetual calendar was developed in such a way that the different lengths of the months are taken into account. The date jumps automatically after the 30th day of short months. Special regulations apply to the month of February as it has fewer than 30 days: for so-called annual calendars, the clock must be manually set in February. A 'half-eternal' calendar on the other hand automatically recognises the shortest month and only has to be corrected every 100 years. Sven Andersen's secular calendar watch even masters the highest discipline: inside it ticks the caliber ETA 2892. This recognises the missing leap year, literally running forever without error. Strictly speaking, only such calendar mechanisms should be referred to as perpetual calendars.
The perpetual calendar – a watchmaking masterpiece
As it is very complicated to always correctly map the Gregorian calendar and build watch calibers capable of taking all exceptions into account, the perpetual calendar is the supreme watchmaking discipline. Together with the tourbillon and minute repeater, it is among the three major complications, the most demanding functions of a mechanical watch. As they are mechanical masterpieces, perpetual calendar watches are very popular with connoisseurs and collectors.
A slimmed-down version of the perpetual calendar is the full calendar. As it does not recognise the length of individual months it must be corrected by hand whenever a month has fewer than 31 days. Often, watches with perpetual or full calendars also have a moon phase display informing the wearer of the current moon phase - full moons, new moons, waning and waxing moons are shown as moon images on a disc shifted daily by a gear wheel. Some watch manufacturers also produce pure moon phase watches. These do not have date displays but dials designed to match the moon theme.
Maintenance and care
Highly complex technology hides inside watches with calendar. This is why it is very important to handle them with care. Definitely protect your model from extreme temperatures: never store your calendar watch in very hot or cold places. You should also pay attention to its water resistance. While some wristwatches can withstand up to several bars, others have to be completely protected from water.
Another important safety precaution concerns the clock's adjustment. Since most clocks switch from one day to the next between 11:00 p.m. and 12:00 a.m., no manual changes should be made during this time otherwise serious damage to individual movement parts can occur. This does not apply to watches such as Ulysse Nardin calendar watches that, according to the manufacturer's instructions, can be adjusted at any time.
The royal discipline of Haute Horlogerie
Watches with a calendar function truly are technical masterpieces. Only calibers with a tourbillon or minute repeater match them in complexity. Accordingly, only the most experienced and respected watch manufacturers include calendar complications in their range of watches.
Patek Philippe is considered a pioneer in the field of calendar watches: in 1941, the first watch with a perpetual calendar was developed and mass-produced in the workshops of this traditional Swiss brand. The raw movement for the remarkable watches came from Valjoux and was built into the legendary model known as 1518. 70 years later, Patek Philippe finally produced its own calibers for calendar watches: the 5270 reference watch was presented at Baselworld in 2011 to the delight of the brand's fans. The technology behind the impressive calendar function has not changed since earlier models: a 'monthly cam' that rotates once around its own axis in the course of a year informs the clockwork about the length of each month. As a result, the date display jumps one, two or three steps further depending on whether it is a month with 30, 29 or 28 days. This clever mechanism requires many carefully processed parts and takes maximum precision in the making of the watch.
Manufacturers of calendar watches
Renowned manufacturers of wristwatches with calendar complications include Audemars Piguet, Jaeger-LeCoultre and Vacheron Constantin. These big names in watchmaking have gained considerable know-how over centuries of producing the most demanding of complications. The renowned IWC Schaffhausen manufactory is also known for being innovative in the field of calendar watches: the 1985 IWC Da Vinci 3750, for example, has a perpetual calendar that can be set using the crown. A further innovation is the calendar mechanism of Ulysse Nardin which can be moved forwards and backwards with the crown. The Patek Philippe brand has also made a name for itself as a manufacturer of high-quality calendar watches with its 5970 model.
Every watch manufacturer realises the high art of calendar technology in its own way, setting different priorities. Most watches with calendars have day, week and month displays but there are also watches with a calendar week display, moon phase display and even day of the week display. Accordingly, among calendar watches, you will find models with simple dials reduced to the essentials as well as those equipped with numerous totalisers and indicator discs. When it comes to design, the manufacturers also use their very own style. The calendar function can often be found on diving watches – popular examples are Breitling Navitimer 1461 and the Omega Seamaster Aqua Terra Annual Calendar.