Mr Roger Dubuis' favourite

The perpetual calendar was a favourite complication of Mr. Roger Dubuis. Attracted by its challenging nature and complexity, he co-patented his own retrograde display in 1989, and in later life, wore a perpetual biretrograde calendar timepiece as his own personal choice.

The mechanical brain

Perpetual calendars have a faultless mechanical memory that keeps track of the day, date, and month, while automatically recognizing months with less than 31 days, as well as leap years. With such a precise brain, the timepiece won’t need programming again until the year 2100 – and then not again for 100 more years. Roger Dubuis perpetual calendars also include the rare independent corrector for the months display.

The 2100 adjustment

This manual adjustment in 2100 is necessary to align our timekeeping more precisely with Earth’s true journey around the Sun.

This precision is achieved through the Gregorian calendar which refines the earlier Julian system that designated every year divisible by four as a leap year. To enhance accuracy, the Gregorian system excludes century years unless they are divisible by 400. As a result, all perpetual calendar timepieces will require a manual adjustment in the year 2100, which, unlike most years divisible by four, will not be a leap year.

The Biretrograde Display

Since the very beginning, most Roger Dubuis perpetual calendars have been identified by their biretrograde display with two ellipsis scales showing date and days, also named “ecliptic counters” by the Maison.

On a retrograde display, the hand moves along a semi-circle scale and returns to its initial position at the end of each cycle. This makes the display playful while also easier to read. Indeed, the hands and indications are larger than on traditional date or day discs.

For Mr. Roger Dubuis, this biretrograde display was the best way to bring expressiveness and dynamism to a complication that is often treated in a traditional way.