Launched in 2012, Rolex’s Sky-Dweller is the brand’s most recent all-new release. It is also, by some distance, the most complicated model in their portfolio. Of course, it doesn’t have that much in the way of competition.

Rolex has built its reputation, and cemented its place at the very top of the horological tree, with watches that are at once enduringly stylish yet technically simple. Until very recently, the Daytona was about as convoluted as they got, or needed to.

But as a way to silence those critics who have long bemoaned the manufacture’s lack of functionality, Rolex’s last two major introductions have taken the company down previously unexplored paths. The model that came before the Sky-Dweller was the Yacht-Master II from 2007, a regatta timer and the only chronograph in the world with a mechanical memory.

As impressive an achievement as the YM II is though, the Sky-Dweller’s combination of GMT function and the first annual calendar Rolex has ever produced takes the prize for most complex watch and the one with the best day-to-day utility.

The Rolex Sky-Dweller

Photo credit: @rolexskydweller

The Sky-Dweller

On the run-up to its unveiling, the only detail known about the Sky-Dweller was its name. Obviously destined to be an aviation-themed creation, it had most fans imagining a tougher, more professional version of the GMT-Master II—sort of like a Sea-Dweller to the GMT’s Submariner.

What arrived instead was more akin to a Day-Date, a dress piece but with a whole host of extra bells and whistles that elevated it straight to flagship status.

It also introduced a novel approach to presenting the dual time feature and a deceptively simple display for its calendar. Even more formidable, it did it all without needing to resort to extra pushers on the case which would have spoiled its sophisticated profile.

Instead, it relinquished control to a very special type of bezel.

The Ring Command Bezel

Photo credit: @rolexskydweller

The Ring Command Bezel

Rotating bezels have been used at Rolex since the mid-1930s, first found on the ultra rare Zerographe. After that, the Turn-O-Graph (otherwise known in the U.S. as the Thunderbird) became the first serially produced model to have one. But of course it became a distinguishing hallmark of the company in the 1950s, when turnable surrounds were fitted to two of watchmaking’s most abiding icons, the Submariner and the GMT-Master.

However, whereas those were used merely to show elapsed minutes or a second time zone, on the Sky-Dweller, the bezel is linked directly to the movement and winding crown, and becomes an integral part of the watch’s capabilities.

It was a similar story on the Yacht-Master II, the model that brought us the first generation of what Rolex dub, the Ring Command Bezel.

On that piece, the bezel is little more than an analogue on/off switch, while on the Sky-Dweller it acts as a function selector, with each quarter turn unlocking a different action.

The first counter-clockwise position gives access to the date. Turning the crown forwards or backwards changes the day of the month in the three o’clock window, and is also used to adjust the annual calendar. Another click to the left and you control the Quickset main hour hand, which jumps in one hour increments. And in the final position, spinning the crown rotates the GMT disc, allowing you to set a reference time as you travel.

The Cal. 9001

The real power behind all the abilities lies in the movement. The Cal. 9001, engineered specifically for the Sky-Dweller, contains some 380 separate parts, making it Rolex’s most component-heavy caliber ever. It is also their second most highly jeweled, with 40, and it has been issued with 7 patents.

Of that colossal parts count, sixty are used for the bezel alone.

The Ring Command module contains a vertically-mounted barrel arbor with switch elements at either end which open up the various operations as the bezel is rotated. A double cam and lever arrangement engages the necessary gear trains at the heart of the movement; pulling out the winding crown activates one cam and the other is driven by the bezel itself, which triggers setting wheels inside the mechanism.

All of the operations can be performed in any order, and either forwards or backwards, with no constraints.

As an example of micromechanics, it is hard to beat, especially considering the size of the Cal. 9001. Measuring just 33mm in diameter, it also manages to pack in a 72-hour power reserve and maintain to within Rolex’s own stringent demands for accuracy of -2/+2 seconds a day.

The Annual Calendar

Photo credit: @watchhabit

The Annual Calendar

For their first foray into the annual calendar complication, Rolex stuck to their basic overriding philosophy of keeping things as simple as possible.

The brand invented the instantaneous date change function in 1945 with the Datejust, and have stayed with the basics of that system here.

The annual calendar, what Rolex have called SAROS after an astronomical term used to predict solar and lunar eclipses, is able to differentiate between the months with 30 and 31 days in them. Therefore, it only needs to be manually adjusted once a year, on the 1st of March, due to February’s 28 or 29 day duration.

To do so has required just four additional gear wheels on top of the traditional date complication. The SAROS is set up so that at the end of a month with only 30 days in it, the date change mechanism provides an extra impulse to the satellite wheel, causing the numbered calendar disc to jump two spaces instead of one, bringing the counter back round to the 1st of the month again.

The Annual Calendar

Photo credit: @rolexskydweller

Twelve small apertures running around the perimeter of the dial, one above each corresponding hour marker, indicate which month it is. Eleven remain blank, while the current month is filled in with a contrasting color. So, a shaded space above the numeral four tells us it’s April, above the five denotes May, etc.

As for the GMT display, that too is a huge departure from the traditional extra hour hand marking out the time on an engraved bezel.

On the Sky-Dweller, an off-centered disc is printed with a 24-hour scale, and a small inverted triangle above it points to the reference time. It is the one visual element of the watch that caused the most controversy on its release, but what was once a challenging aesthetic seems to have matured with age—helped along by a series of more conservative and monochromatic color schemes being made available.

The Rolex Sky-Dweller

Photo credit: @rolexskydweller

A New Direction?

Without the ability to predict what Rolex has in store for us in the future, it is impossible to know whether the Sky-Dweller is the start of a whole new breed of complicated watches, or whether it is something they created almost just to prove to the doubters they could.

What is sure is that it is an incredible example of engineering virtuosity that manages to provide a massive amount of information in an elegantly tasteful way.

It is also a real traveler’s watch. The winding crown is notoriously the weakest part of any mechanical timepiece. By confining it to only two positions, one for winding and the other for setting all the functions, the Sky-Dweller has an inherent strength that means it can survive the knocks that are an inescapable part of international globetrotting.