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6 Calendar Complications that Range from Simple to Ultra-Complex

The Patek Philippe Ref. 5261R-001 Aquanaut Luce Annual Calendar in pink gold.

Calendrical complications span from everyday functionality to microengineering feats, underscoring the multifaceted world of mechanical watchmaking.

The basis of horology was formed by looking at the sky and examining the solar and lunar cycles. These astronomical schedules inform our social and cultural activities, measured mechanically by horologists. Early mechanical clocks provided complex calendrical displays such as the date, day, month, moon phase, zodiac sign, and more.

Globally, the Gregorian calendar is the standard, and its various required adjustments make its presentation in the confines of a wristwatch a bit of an engineering challenge. Calendar complications range from the simple to haute horlogerie, providing watchmakers with the opportunity to flex their creative and technical muscles. These six watches feature different calendars, each with highly legible designs.

1. Big Date

The A. Lange & Söhne Lange 1 in white gold has an off-centre, outsized date display.
The A. Lange & Söhne Lange 1 in white gold has an outsized date display.

The concept of displaying the date on two adjacent discs dates back to the 18th century. On the wristwatch, this style was popularised by A. Lange & Söhne in 1994. Two discs, one for the tens and another for the ones, are controlled by a separate gear system and activated at midnight for the date jump. The Saxonia Outsize Date may be the purest expression of this complication, but it is most pronounced in the Lange 1. The numerals are about three times larger than the typical date window and housed in a large golden frame. The design of the Lange 1 follows a mathematical principle: all displays are arranged off-centre, forming an isosceles triangle.

2. Triple Calendar

The Jaeger-LeCoultre Master Control Chronograph Calendar in pink gold with black dial.
The Jaeger-LeCoultre Master Control Chronograph Calendar in pink gold with black dial.

A triple or complete calendar displays the day of the week, date, and month with the option of a moonphase indicator. Considered a gateway to the endless options of more complicated calendar watches, a complete calendar still requires some adjustments. In months with less than 31 days, you must advance the date manually. In Jaeger-LeCoultre’s Master Control Chronograph Calendar, the indicators – which include a disc for the moonphase display – are balanced in a dial layout that is supremely legible. A pulsometric scale marked around the dial flange, a traditional indication to measure heart rate, adds to the vintage appeal of this elegantly designed 40mm watch. Powered by the automatic Calibre 759, the Master Control Chronograph Calendar is available in pink or white gold with an easy-change strap.

3. Annual Calendar

The Patek Philippe Ref. 5905R-010 Annual Calendar Chronograph in pink gold.
The Patek Philippe Ref. 5905R-010 Annual Calendar Chronograph in pink gold.

Patek Philippe’s annual calendar complication, created in 1996, was intended to cater to watch buyers who desired an innovative, user-friendly, and relatively accessible complication. This ingenious mechanism, which has emerged as one of the Manufacture’s flagship complications, requires just one correction per year at the end of February. While there are several calendar-only models, a favoured combination is the annual calendar with flyback chronograph – a step down from Patek Philippe’s famed perpetual calendar chronographs. The Ref. 5905 comes in a new rose gold version with a sunburst blue dial – a vivid display of modern elegance. The day, date, month and day/night indications are presented in apertures in the upper quadrant of the dial, while the chronograph minutes totaliser is at the 6 o’clock position.

4. Perpetual Calendar

The Piaget Polo Perpetual Calendar Ultra-Thin in white gold case with obsidian dial and sapphires on the bezel.
The Piaget Polo Perpetual Calendar Ultra-Thin in white gold with blue obsidian dial and sapphires on the bezel.

Invented by English watchmaker Thomas Mudge in 1762 and first put in a wristwatch by Patek Philippe in 1925, the perpetual calendar complication or quantième perpétuel was given the ultra-thin treatment last year by Piaget. The perpetual calendar colloquially goes by ‘set and forget’ because it has a mechanical memory of 1,461 days, accounting for the leap day of February 29. Just don’t forget to keep the watch wound. Piaget’s Polo Perpetual Calendar Ultra-Thin is powered by the new ultra-thin Calibre 1255P, which resides beneath a gadroon-patterned emerald-green or blue obsidian dial on the gem-set model. Super-LumiNova-filled hands glide over sub-dials for the date, month plus leap year, and day at 9, 12 and 3 o’clock, respectively, along with a highly minimalist moonphase display at the 6 o’clock position.

5. Secular Perpetual Calendar

Audemars Piguet's Code 11.59 Ultra-Complication Universelle RD#4 offers a highly legible calendar indication for the highly complex watch.
Audemars Piguet’s Code 11.59 Ultra-Complication Universelle RD#4 offers a highly legible calendar indication for the highly complex watch.

Most perpetual calendars require a correction every centennial year that is not divisible by 400 when the Gregorian calendar omits a leap year. This means a manual adjustment is required in the years 2100, 2200, and 2300. The secular perpetual calendar adds a mechanism to account for these differences, making it accurate to 9,999 years instead of 100. Patek Philippe was the first to introduce a secular perpetual calendar in a wristwatch in 1972, but more recently, Audemars Piguet has improved on it in the Code 11.59 Ultra-Complication Universelle RD#4. The GPHG award-winner packs 40 functions and 23 complications in one movement, and the 42mm watch is incredibly easy to read and sublimely comfortable to wear.

6. Equation of time

The Bovet Récital 20 Asterium in white and red gold case.
The Bovet Récital 20 Astérium in white and red gold.

What is an Equation of Time (EOT)? Essentially, it is the difference between the time you see on your watch (mean solar time) and a sundial (apparent solar time). This discrepancy is because of Earth’s tilted axis and elliptical orbit. Thus, the sun appears to speed up and slow down over the course of a year. One way to show an EOT complication is by using a sub-dial with a hand that indicates the variance of apparent solar time to mean solar time. A second minutes hand can also be used to indicate the difference. Over the course of a year, the EOT hand slowly overtakes and then falls behind the normal minute hand following our planetary orbit.

Bovet’s Récital 20 Astérium, another GPHG winner from last year, uses a sub-dial to the left of the celestial and time display to indicate the EOT. The constellations of the sky are laser-engraved on a dome of translucent blue quartz and filled with Super-LumiNova.

From the practical to the sophisticated, calendrical complications demonstrate the broad spectrum of mechanical watches that are available today. And there’s more, from lunar calendars to tidal watches. The question is, which suits your lifestyle best?