IWC Aquatimer Perpetual Calendar Digital Date-Month



Limited to just 50 watches, the Aquatimer Perpetual Calendar Digital Date-Month combines state-of- the-art technology with quality looks. Hidden away inside the case made of unusual materials such as rubber-coated titanium and 18-carat red gold is a perpetual calendar with a large digital display showing the date and month. The integrated quick-action switch, which advances the month display, has one thing in common with the Galapagos marine iguana: they are both masters of energy efficiency.

Several million years ago, a number of iguanas landed by chance on the Galapagos Islands. Unable to find enough food on the barren archipelago, they turned to the oceans for sustenance. But in the cold water, their body tempera- ture sank rapidly. Over time, the marine iguanas became masters of energy efficiency: they bask in the sun on the baking hot volcanic rock, storing the energy they need  for their strength-sapping dives; once in the water, they reduce their energy requirements by slowing down their heartbeat. This is nature’s way of showing us how to use energy intelligently. Energy plays a central role not only in biology but also in watchmaking mechanics. The auto- matic winding system in a mechanical watch supplies the movement with energy, but owing to the limited length of the mainspring, only part of it can be saved. There is enough energy for basic timekeeping and even for energy-sapping complications like the perpetual calendar. But if the per- petual calendar in question has large digital date and month displays with an additional leap year display, it means five display discs may need to be moved simultaneously. And this is where a conventional winding mechanism is soon stretched to its limits. For this reason, the engineers at IWC Schaffhausen developed the quick-action switch. This self- contained mechanical energy storage device builds up the power required to advance the month display discs con- tinuously throughout the month. A special cam raises the spring-loaded lever on the quick-action switch a little bit further each day. At the end of the month, when the spring 
is under maximum tension, it is time for a decisive act of strength: the quick-action switch jumps instantly to its start- ing position and, depending on the month, advances the two month display discs either singly or synchronously. At midnight on New Year’s Eve, the same system also moves the leap year disc. Needless to say, all without any effect on the movement’s accuracy. Storing energy and being able to access it as needed: the quick-action switch and the marine iguana function according to the same principle.


In 2014, the perpetual calendar with its quick-action switch and large digital display showing the date and month took its place in IWC Schaffhausen’s diver’s watch family. Limit- ed to just 50 watches and available exclusively in IWC boutiques, the Aquatimer Perpetual Calendar Digital Date-Month (Ref. IW379401) is the flagship of the new Aquatimer collection. The distinctly technical design of the dial is characterized by the extra-large numerals of the per- petual calendar, which is mechanically programmed until 2100. The date and month discs have perforated covers. The designers took their inspiration for this particular element from the filter systems that are omnipresent on submarine vehicles. This provides a view of the complex switching mechanism at work: a fascinating spectacle, particularly  at the end of the month, when all four date discs move simultaneously. The four-year leap year cycle is also shown digitally. At IWC, the digital display with large numerals has a tradition dating back over 100 years: the company’s first pocket watches with a jumping digital display had their market launch as long ago as 1884. The Pallweber watches,  named after the holder of the patent, were initially very popular. Unlike the date, however, the digital time display never really caught on. Even today, most individuals prefer an analogue display with hands because it is easier and more intuitive, and gives a better sense of time periods. IWC’s engineers made use of this fact in the Aquatimer Perpetual Calendar Digital Date-Month with its second  innovative form of indicator, the chronograph display. This gives you an easy, convenient way of sticking to the pre- scribed surface interval time between your first dive and the next. A subdial at “12 o’clock” displays stop times be- tween one minute and 12 hours as simply as the time of day, using minute and hour hands, while the central hand counts the number of seconds. Anyone who has experienced an analogue stopwatch will only reluctantly go back to ag- gregate timing using two or more counters. The integrated flyback function enables the user to reset the running stop- watch hands to zero and to start another timing sequence immediately. The display also helps divers monitor the speed of their ascents.


With regard to either the digital date display or the case, the Aquatimer Perpetual Calendar Digital Date-Month is  a genuinely big watch: with an impressive diameter of  49 millimetres, it is the second-largest wristwatch in IWC’s history after the Big Pilot’s Watch of 1940. The external rotating bezel is made of 18-carat red gold, as is the pro- tective cover on the left side of the case for the advanced sliding clutch system, which transmits the rotation of  the external bezel to the internal rotating bezel. The IWC  SafeDive system ensures that the bezel can only be turned anticlockwise, and that zero hour – a dive time requiring no decompression stops – is not inadvertently exceeded. The casing ring, push-buttons and crown are made of rubber-coated titanium. While the attractive black rubber strap with its black alligator leather inlay guarantees max- imum comfort in wear and a long service life, the unusual combination of red gold, rubber and leather gives the watch a look that is both classy and sporty at once. The see-through sapphire-glass back provides a view of the IWC-manufactured 89801 movement, which comprises 474 individual parts, and its highly efficient double-pawl winding mechanism. The rotor has a distinctly functional look and feel and alludes to the reliability of research sub- marines. The Super-LumiNova®* coating on the hands and indices glows particularly brightly in the dark in two different  colours: green for displays relevant to dive time, blue for the hour display. The imposing Aquatimer Perpetual Cal- endar Digital Date-Month is water-resistant to 10 bar and will attract attention both underwater and on terra firma:  another feature it has in common with the marine iguanas on the Galapagos Islands.

* IWC Schaffhausen is not the owner of the Super-LumiNova® trademark.

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REF. IW379401

Mechanical chronograph movement – Mechanical external/internal rotating bezel with IWC SafeDive system – Perpetual calendar – Large double-digit displays for both the date and month – Leap year display – Stopwatch function with hours, minutes and seconds – Hour and minute counters  combined in a totalizer at 12 o’clock – Flyback function – Small hacking seconds – Luminescent elements on hands, dial and internal rotating bezel – Screw-in crown – See-through sapphire-glass back – IWC bracelet quick-change system – Limited to 50 watches


  • IWC in-house calibre 89801
  • Frequency 28,800 A/h / 4 Hz
  • Jewels  51
  • Power reserve  68 h
  • Winding  automatic 


  • Materials  casing ring made of rubber-coated titanium, external rotating bezel in 18-carat red gold, case back made of 18-carat red gold and sapphire glass, black dial, black rubber strap with alligator leather inlay, pin buckle in red gold
  • Glass sapphire, convex, antireflective coating on both sides
  • Water-resistant 10 bar
  • Diameter  49 mm
  • Case height 19 mm