The Most Accurate Moonphase Watch in the World

In the world of high-end horology, moonphase complications are more than just a romantic nod to the night sky. They’re a showcase of mechanical precision. Most traditional moonphase watches display the lunar cycle using a 59-tooth gear, which approximates the moon’s 29.5-day cycle. But this setup causes a small inaccuracy: after about 2.5 years, the phase display will be off by a full day. However, some watchmakers have taken this poetic complication and engineered it to a level of staggering accuracy. Take the Andreas Strehler Sauterelle à Lune Perpétuelle 2M, which holds the title for the most accurate moonphase watch ever made. This Swiss marvel is so precise that its moonphase will remain accurate for 2,060,757 years before it needs a single correction. To put that in perspective, the pyramids of Giza are only about 4,500 years old. The movement achieves this by using a high-precision gear ratio that perfectly accounts for the synodic lunar month: 29 days, 12 hours, 44 minutes, and 2.8 seconds. Every tooth, wheel, and ratio is finely tuned to astronomical data. The watch’s accuracy was verified by Witschaftsförderung Region Ostschweiz, an official Swiss regional innovation agency that certifies technical innovation and precision. The watch was awarded for its engineering feat, combining centuries-old craftsmanship with cutting-edge mathematical modeling. Other notable entries in this rare club include the A. Lange & Söhne Richard Lange Perpetual Calendar “Terraluna,” which is accurate to one day every 1,058 years, and the De Bethune DB25 Moon Phase, accurate to within one day every 1,112 years. While these watches come at a steep price, they represent something rare in modern life: mechanical art that outlasts generations.