With February 29 being that special day which occurs once every four years due to being part of a leap year, we at Revolution decided to take a look at some of the Perpetual Calendars that mattered throughout watchmaking history. Concluding our look-back series is the Audemars Piguet Royal Oak Selfwinding Perpetual Calendar Ultra-Thin, a timepiece which ushers this classical complication into the modern era and possibly into the future of perpetual calendars.

As we have previously mentioned in this series of stories, Audemars Piguet is known to have produced the first series of perpetual calendar wristwatches with a leap year indicator in 1955. The brand is often praised for making some of the most elegant perpetual calendar watches available, and has an illustrious uninterrupted history of creating exceptional calendar watches. At the height of the Quartz Crisis, with the Swiss watch industry in bad shape, the brand trusted their abilities in creating mechanical timepieces and to innovate by releasing the world’s thinnest self-winding perpetual calendar wristwatch in the late 1970s; bringing success and stability for the company. Finding growth at a time when barely anyone was producing complicated watches and was shying away from traditional watchmaking, is a testament to Audemars Piguet’s technical know-how and craftsmanship. This led them to introduce many variations of their perpetual calendar watches in the years that followed and in a variety of case designs ranging from the Jules Audemars to the iconic Royal Oak.

Presented at SIHH 2018 in a prototype form, the new Audemars Piguet Royal Oak Selfwinding Perpetual Calendar Ultra-Thin, dubbed the RD#2, saw its production release at the end of 2019. The 41mm case size is identical to the current generation perpetual calendar Royal Oak, but the total height of the case has been reduced to 6.3mm. To put that into perspective, know that the recently released 41mm self-winding Royal Oak ref. 15500 has a case height of 10.4mm, the existing Royal Oak Perpetual Calendar is 9.5mm thick, and the 39mm Royal Oak “Jumbo” extra-thin comes in at 8.1mm.

Audemars Piguet Royal Oak Selfwinding Perpetual Calendar Ultra-Thin (Image © Revolution)
Audemars Piguet Royal Oak Selfwinding Perpetual Calendar Ultra-Thin (Image © Revolution)

To achieve this incredible low height of 6.3mm – with the movement inside – Audemars Piguet re-worked its caliber. It took the smartest people at AP – we’re talking engineers, designers, programmers and watchmakers – to push the limits of their craft to re-engineer the perpetual calendar movement as we know it. Where the perpetual calendar functions are normally arranged on three levels, they have now been merged into a single layer by integrating the end-of-the-month cam into the date wheel, while the month cam has been combined with the month wheel. This resulted in the all-new Caliber 5133 with a mind-blowing total thickness of only 2.89mm – and with a full rotor, s’il vous plaît. Of course these new innovations have been patented, paving the way for a future generation of thin and complicated watches.

The dial does away with the classic tapisserie pattern and is replaced by a dark blue satin finish which is brushed vertically. This has the advantage of making the watch look thinner on the eyes and to make it stand out visually from the other perpetual calendar Royal Oak watches. The case and bracelet are in titanium with the centre links and bezel in polished platinum. The result is an attractive juxtaposition of the two metals. The polished platinum bezel almost disappears under certain lighting conditions, which makes the watch look even thinner than it actually is.

Audemars Piguet Royal Oak Selfwinding Perpetual Calendar Ultra-Thin (Image © Revolution)
Audemars Piguet Royal Oak Selfwinding Perpetual Calendar Ultra-Thin (Image © Revolution)
Audemars Piguet Royal Oak Selfwinding Perpetual Calendar Ultra-Thin (Image © Revolution)

All in all, the Royal Oak Selfwinding Perpetual Calendar Ultra-Thin is a great demonstration of Audemars Piguet’s ability to innovate and usher watchmaking into a modern era of technical performances. One can only speculate which next complication AP will manage to reduce in thickness but there is no doubt that this watch will serve as the launching pad for a whole new generation of ultra-thin complicated watches.

Audemars Piguet Royal Oak Selfwinding Perpetual Calendar Ultra-Thin (Image © Revolution)