From Here To Eternity: Understanding The Perpetual Calendar
What is a perpetual calendar watch? And why do we need it to run long after we've gone?
IT IS THE MOST UTILITARIAN OF COMPLICATIONS
If one were to rank the four major watch complications – tourbillon, minute repeater, chronograph and perpetual calendar – in order of practicality, the perpetual calendar will surely emerge at the top of the pile. “The tourbillon and minute repeater are definitely more difficult to construct. But I like the perpetual calendar for its functionality. It is not something to play with. It’s a watch to wear and to use,” says Kurt Klaus of IWC, inventor of the arguably the most famous perpetual calendar movements in contemporary watchmaking.
IT IS THE ULTIMATE CALENDAR WATCH
A perpetual calendar’s core functions are to tell the time and everything that relates to the calendar information at a single glance. By that, we mean the day, date, month and moon phase, plus the automatic correction of month lengths and leap years.
In normal calendar watches, the date mechanism counts from 1 to 31. So, if a month has less than 31 days, it needs to be manually adjusted. And here is why the perpetual calendar is so amazing – the mechanism has a way of calculating how many days there are in a month, including those in leap years. Also, where simple calendar watches usually have to be corrected five times a year (after each month with fewer than 31 days), the perpetual calendar relies on a mechanical memory with a reserve of usually more than four years.
THE TECHNICAL BIT...
The perpetual calendar features a differential gear mechanism that comprises separate sets of wheels, gears, levers and discs for each of its four main functions (date, day, month and moonphase). This is why perpetual calendars tend to require multiple pushers to reset each of these functions if the watch stops.
DON'T WORRY, SOME ARE EASY TO USE
Most collectors will point you to IWC’s Da Vinci automatic chronograph perpetual calendar with the Calibre 79261, designed by Klaus and launched in 1985, as one of the easiest perpetual calendars to use. Retailing at half the price of its nearest competitor back then, with an improved design that lets one adjust all its indications easily via a single crown, along with unique signatures like a four-digit date display, the Da Vinci effectively cemented its place in history as one of the most savvy perpetual calendar constructors.
AND THE MOTHER OF ALL PERPETUAL CALENDARS IS...
This 1925 model from Patek Philippe. Bearing the reference No. 97975, it featured an instantaneous jumping perpetual calendar and moon phase display and age of the moon. According to archives, the movement was constructed in 1898 and had never been used until it was fitted in this wristwatch.
OH, AND IT'S CONSTANTLY EVOLVING
Legibility and ease-of-use are the holy grails of perpetual calendar watches, and watch companies have strived to make these timepieces with functionality as top priority. Some recent outstanding innovations include H. Moser’s Perpetual 1, which features possibly the most stripped-down perpetual calendar display you’ll ever see; A. Lange & Sohne’s Grand Complication with a perpetual calendar mechanism that advances all displays, with the exception of the moon phase, at the stroke of midnight; and MB&F’s Legacy Machine Perpetual (pictured) that purports to be more robust, thanks to its fully integrated architecture that eschews the traditional module-based construction approach.
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