Among watch complications, the perpetual calendar ranks among the most technically demanding. It tracks varying month lengths and leap years, enabling a correctly set watch to display the date until 2100, when the Gregorian calendar skips a leap year. Such precision relies on a complicated and compact mechanical memory of gears, levers, and cams, which is why only a select few manufactures have mastered it.
Roger Dubuis is one of those notable brands. Perpetual calendars were a cornerstone of the founder’s work, so much so that he wore a perpetual biretrograde calendar as his personal timepiece, a sign of how central the complication was to the maison’s early identity.
The biretrograde display is a signature in its own right, though not exclusive to the perpetual calendar. Roger Dubuis co-patented it with master watchmaker Jean-Marc Wiederrecht in 1989 and brought the format to the wristwatch in 1996. Rather than conventional sub-dials or windows, the day and date indicators glide along elliptical scales before snapping back to their starting point, a dramatic effect that is distinctly Roger Dubuis. When this is applied to a perpetual calendar, it makes the display quick and easy to read.
That pioneering tradition continues this year at Watches and Wonders Geneva, where the Excalibur Biretrograde Perpetual Calendar dominated with a new calibre and an astronomical moonphase for the first time.
The watch is driven by the RD850, a refined biretrograde perpetual calendar movement comprising 435 components and offering a 60-hour power reserve. Its key practical update is a month corrector, allowing single-step adjustments rather than multiple advances through the mechanism. Although a minor change on paper, it significantly speeds up setting the watch and reduces wear on the movement.
At 6 o’clock, the calendar is paired with an astronomical moonphase, precisely calibrated to the moon’s orbital cycle of 29 days, 12 hours, and 45 minutes—not the simplified 29.5-day cycle common in many moonphase mechanisms. Over time, a standard display may drift by a day after about two to three years, whereas Roger Dubuis’ design remains accurate for approximately 122 years before a one-click adjustment is needed.
The RD850 bears the Poincon de Geneve, certifying its Genevan origin and exceptional finishing. The movement features 16 types of finishes, including hand-finished inner angles. This is among the most demanding techniques as the angles are shaped and polished by hand with specialised tools. On the Excalibur Biretrograde Perpetual Calendar, 14 of these polished inner angles are seen on the W-shaped retrograde bridges at 3 and 9 o’clock.
The open-worked dial comprises nine layers and is finished in a new Astral Blue hue, reminiscent of a distant galaxy. From the outside inwards: a double-surface azure flange, Astral Blue mother-of-pearl counters with polished edges, a matching month disc, a circular-brushed grey leap-year indicator at 1 o’clock, and a circular-brushed grey main plate.
The moonphase counter is crafted in Astral Blue mother-of-pearl, with a moon disc in aventurine and a domed pink gold moon, laser-engraved to add texture. Beneath the dial, the open-worked calibre is visible, revealing hand-finished retrograde bridges and a sun-brushed grey main plate module. The watch is offered in a 40-mm pink gold case paired with a matching Astral Blue calfskin strap.
