How often do you set your watch? Your answer likely depends on how much you wear it. If you only use it occasionally, it’s likely you set it each time you pick it up. But if you sport the same watch daily (or keep it on a winder when not in use), you probably only adjust it when you notice a deviation. Annual calendar and perpetual calendar watches have made this task easier, but unless you’ve sworn off everything save for digital pieces, setting the time is a fact of watch ownership. And as collectors of vintage watches with no quick-set date can attest, laboriously spinning forward the hands just to get the date window correct can make even the most hardened aficionado weep. So, we were understandably interested when IWC announced its new Eternal Calendar is accurate for 45 million years. Well, the moon phase is, at least. The perpetual calendar complication? Your fiftieth great-grandchild might have to adjust once in the year 4000. Still, the new IWC Portugieser Eternal Calendar watch is a remarkable achievement in watch movement design, and we saw it hands-on at Watches & Wonders 2024.

This mind-boggling capability has more to do with super-computing than the automatic mechanical movement might suggest. By using software to simulate trillions of gearing combinations, IWC was able to identify a sequence that would provide the right system of timekeeping to enable the Eternal’s long-lasting accuracy. Of course, such breakthroughs in horology ought to be paired with equally noticeable aesthetics and on the dial, they certainly are. While the arrangement of IWC perpetual calendar dials have always been captivating for both their symmetry as well as simplicity, the Eternal tweaks this approach, removing the seconds-track from the subdial at 9 o’clock, and updating the double-moonphase indication. Here, an understandably braggadocious label helps solve the cut-off numeral problem, replacing the chopped “12” with an “Eternal Calendar” branding. Left and right of the moonphase, the hemisphere indicators have also been simplified by the removal of the “N” and “S” labels, instead relying on intuitively shaped semi-circles to tell which part of the moonphase corresponds to the northern and southern hemispheres. Color has also been deleted, with the seven-day power reserve taking on a monochrome look that matches the dial’s overall appearance. All these updates connect in their own way to the biggest part of the Portugieser calendar’s refresh — the glass/lacquer construction that makes the dial text appear to be floating. Starting with a thick glass dial, IWC has coated the underside with white lacquer, then printed the text and applied the silver numerals on top. When paired with other dimensional elements like the hands, separate double-moonphase indicator, and a stepped cut-out at 4 o’clock, the Eternal’s dial takes on a depth that gives it an unmistakable character.