his new calendar features several innovations, including the ergonomics of the case but most of all the date setting... as there is only one crown!” We are in Le Brassus at the beginning of 2025, the year of Audemars Piguet’s 150th anniversary, and Giulio Papi, its Director of Watch Conception, greets us, with his colleagues, in a room whose intimate proportions contrast with the vast, luminous, open spaces of the imposing new Arc building.

It’s here that we discover the ingenuity of this automatic perpetual calendar – and what better way to celebrate an anniversary than with a calendar! “Until now, setting a perpetual calendar required a certain amount of skill on the part of customers and could be frustrating,” explains Giulio Papi. “We saw people using any object to set the correctors, even a toothpick, which is a shame because we ended up with timepieces that no longer showed the proper indications, or were even damaged.”

The Royal Oak Perpetual Calendar 25554 featured on the front page of a 1984 Europa Star article on calendar watches. ©Archives Europa Star

Enter Calibre 7138, a new generation of automatic perpetual calendar movement which, for the first time, allows each of the watch’s functions to be set using an “all-in-one” crown, thereby doing away with the traditional correctors on the side of the case. This new movement makes its debut on a 41mm Code 11.59 by Audemars Piguet in 18k white gold, on two 41mm Royal Oak models in a choice of stainless steel or 18k sand gold, and on three corresponding “anniversary” limited editions of 150 pieces.

“It took five years to develop this calibre and we have filed five patents,” continues Giulio Papi. “One prerequisite was to make good progress in the field of ultra-thin watches, in order to house all the components of this new system while maintaining the same thinness, enabling the movement to keep a thin 4.1mm profile.” For all the corrections to be made at the crown required a complete redesign of the movement. But how does it work, exactly?

From 3 to 2’

The new crown incorporates four different positions. The first enables the user to wind the watch clockwise. Pulling the crown out one step (position 2) allows them to set the date clockwise and to adjust the month and the leap year in the opposite direction. By pulling the crown out again (position 3), the user can set the time bidirectionally. The last position is reached by pushing the crown back one step (position 2’) to set the day and week clockwise and the moon phases counterclockwise.

“A single crown thus adjusts six functions, four of which are for the perpetual calendar,” summarises Giulio Papi. The simplicity of the new crown correction conceals, however, a complex mechanism driven by an innovative lever and wandering wheels system that meshes with the different calendar wheels in the 2 and 2’ positions. This innovation is protected by two patents: one for the crown correction system with a 2’ position and one for the month and date correction via the crown.

As all calendar functions are synchronised thanks to the new crown correction system and more robust movement construction, it is impossible to desynchronise the watch and damage the mechanism if the user tries to set their watch when the automatic date change mechanism is active (between 9pm and 3am).

The dial and subdials have been rearranged to enhance legibility, symmetry and aesthetic harmony. The dial now features a European date display, with the day at 9 o’clock, the date at 12 and the month at 3 o’clock. The week numbers are printed on the inner bezel, as for previous perpetual calendar models. However, it is now the first week of the year (1) that appears at 12 o’clock (instead of week 52).

For its 150th anniversary, Audemars Piguet presents a revolutionary perpetual calendar that is fully adjustable by the crown: Calibre 7138.

In the same logic, Monday and 1 have been aligned at 12 o’clock in their respective subdials to mark the start of the week and the first day of the month. The dial also features a patented progressive step for the date display at 12 o’clock. The Audemars Piguet teams developed a date wheel with 31 custom-made teeth, the size of which varies to adapt to the width of the digits and enhance readability.

To achieve perfect symmetry with the subdial at 3 o’clock, which indicates the month and leap year, a 24-hour indicator has been inserted in the day subdial at 9 o’clock. In addition, a no-correction zone is marked in red between 9pm and 3am to show when the watch cannot be set (although, as mentioned, if the user does attempt to set the watch during this time, there is no risk of damaging the movement).

The moon phase, which displays a realistic depiction of the moon based on a NASA photograph, remains at 6 o’clock as for previous references. However, the full moon is now centred on the 12 o’clock axis to strengthen the dial’s overall harmony.

Assuming the watch is kept fully wound, the date will not require manual correction until the year 2100, when it will need to be adjusted to stay in line with the Gregorian calendar. The Gregorian calendar omits three leap years every 400 years, to keep in sync with solar time. This is achieved by omitting February 29th in the century years that are divisible by 100 but not by 400. As a result, 2100 will not be a leap year and perpetual calendar mechanisms will have to be moved forward by one day.

One of Audemars Piguet’s favourite complications

The Manufacture is far from being in uncharted territory in developing this innovation on the perpetual calendar, this “small mechanical computer” as Sébastian Vivas, Heritage and Museum Director at Audemars Piguet, calls it. Its expertise in astronomical complications started with the two founders’ school pocket watches, both completed around 1875.

The first Audemars Piguet complete calendar wristwatch was put into production in 1921 and sold three years later to the renowned retailer Gübelin. From 1921 to 1970, 188 complete calendar wristwatches were produced – a small part of the Manufacture’s total production during these years.

A turning point came in 1955, when the company released the world’s first perpetual calendar wristwatch with leap year indication, nine examples of which were created between 1955 and 1957. It broke another record in 1978, at the height of the quartz crisis, with the world’s thinnest automatic perpetual calendar wristwatch of its time, Calibre 2120/2800.

For its debut, Calibre 7138 launches simultaneously on a 41mm Code 11.59 by Audemars Piguet in 18k white gold, and two 41mm Royal Oak models in a choice of stainless steel or 18k sand gold.

Conceived in secret by three watchmakers, this groundbreaking perpetual calendar movement achieved its extra-thinness (3.95mm) by using the ultra-thin Calibre 2120 (2.45mm thick), launched in 1967, as its base. Over the next 18 years, more than 7,000 movements were produced, cased and sold, ushering in a new era of growth for the brand and paving the way for the revival of classical complications. In 1984, this calibre powered the first Royal Oak Perpetual Calendar (39mm in diameter), Model 5554, soon followed by other references in the collection.

This classic complication was somewhat in decline in watchmaking at the end of the twentieth century and the beginning of the twenty-first. It was revived in 2015 with Calibre 5134: it adapted the perpetual calendar movement to a larger 41mm case diameter, while maintaining a thin profile of 4.3mm. It was first housed in a new Royal Oak model with a dynamic aesthetic.

This revival was confirmed in 2017 with the release of the Royal Oak Perpetual Calendar 26579CE in black ceramic, which caused a sensation. This calibre powered numerous perpetual calendar wristwatches across the Manufacture’s collection until 2024, when it was retired. It was last featured on the Royal Oak Perpetual Calendar “John Mayer” Limited Edition, bringing down the curtain on a story that began in 1978.

In 2018 the Manufacture opened yet another chapter in its history of perpetual calendar timepieces with the launch of the revolutionary 41mm Royal Oak Selfwinding Perpetual Calendar Ultra-Thin, known as RD#2 – the world’s thinnest automatic perpetual calendar wristwatch of its time. This 6.3mm-thick watch houses Calibre 5133, an ultra-thin movement measuring just 2.89mm in height, which was fully redesigned to incorporate all the perpetual calendar functions on one single level, heralding a new generation of astronomical watches.

It is thanks to this rich history, and more particularly the patented innovations that enabled the creation of the RD#2, that the all-new Calibre 7138 sees daylight, with simplified use thanks to adjustment by the crown alone. A new era is dawning, right on time, in the calendar of the Le Brassus-based Manufacture.