09/14/2021
 4 minutes

The MB&F LM Perpetual: A Perpetual Calendar Like No Other

By René Herold
MBFPerpetualCalendar-Magazin-2-1

The perpetual calendar belongs to an elite class of watch complications. It can automatically account for differing month lengths, including in leap years! If you set the date correctly and supply the watch with enough energy, you won’t have to manually correct your perpetual calendar until 2100 (the next secular year that drops the leap year). 

Perpetual calendars have been around since the 17th century. The complication was initially built into grandfather clocks and later into pocket watches. The first wristwatch to feature a perpetual calendar was a Patek Philippe timepiece released in 1930. Countless manufacturers now offer watches with this complication, most built using the same historical techniques. While quite a lot of energy has been invested into optimizing the design and improving the production quality of the complication in the past 50 years, perpetual calendars today don’t differ much from their ancestors. This means that contemporary watches with a perpetual calendar function still struggle with the same weaknesses as their historical predecessors.  

Sensitive and Prone to Error 

One of the biggest disadvantages of the perpetual calendar is its high level of sensitivity and susceptibility to error. For example, you can irreparably damage the delicate mechanism if you adjust the time while the date is changing. Another shortcoming is how the mechanism jumps from months with less than 31 days to the 1st of the following month. Traditionally, this is done via a Grand Levier rocker switch that stretches across the complication and synchronizes the individual calendar displays when the date changes. The problem with the classic perpetual calendar design is that it assumes all months have 31 days. During shorter months, the rocker switch has to “skip” over some days. In practice, this means the mechanism has to move several times in quick succession. For example, at the end of February, the rocker switch has to jump four days from the 28th to the 1st at lightning speed. It is not uncommon for the gear to slip too far or too little in these instances. If this is the case, the watch will display the incorrect date, and you will have to manually correct it – precisely what the perpetual calendar is supposed to prevent.  

The rocker switch has yet another disadvantage: It lies across the center of the complication and requires space to move freely. This means nothing can be attached to it that will hinder its movement. The pins used to hold skeletonized dials in place, for example, are not an option. This is further complicated by the fact that most perpetual calendars are modules added to base movements, which places more restrictions on the space available. Thus, watches with perpetual calendars traditionally have closed dials with several small windows for the date, day, etc. 

MB&F Rethinks the Perpetual Calendar  

These inadequacies are what kept Maximilian Büsser (founder of the innovative watch manufacturer MB&F) from offering a watch with a perpetual calendar for some time. However, MB&F teamed up with master watchmaker Stephen McDonnell to completely rethink the perpetual calendar. The result is a caliber that fully integrates the complication and is comprised of 581 individual components. 

McDonnell did away with the traditional rocker switch and developed a mechanical processor consisting of several plates stacked on top of one another in its place. The design doesn’t just save space; it also allows for more freedom in the movement configuration. However, the most ingenious thing about this mechanical processor is that it assumes each month only has 28 days – the minimum number of days in any given month. For months with more than 28 days, the extra days are “added,” which prevents the problem of days accidentally being skipped.  

The processor also has a built-in safety feature that deactivates the calendar buttons as soon as the date-changing process begins. This prevents any damage from occurring due to an accidental press of a button.  

Yet another special feature is the way you correct the leap year. Thanks to a special cam, you only need to press a single push-piece to adjust the leap year. With conventional perpetual calendars, you’d have to manually jump forward as many as 47 months until you arrived at the right combination of month and year.  

The Legacy Machine Perpetual: Now Available in Palladium 

The movement first appeared in 2015 in the MB&F Legacy Machine Perpetual. The watch has since been offered in yellow, white, and rose gold, as well as platinum and titanium. The manufacturer has now added a new variant in palladium. Like all the other versions, this new model is a feast for the eyes of any watch enthusiast. The caliber is particularly stunning with its large balance wheel set on a V-shaped bridge in the center of the skeletonized movement. MB&F moved the escapement to the back of the watch. This is made possible by an extra-long balance shaft that runs through the entire movement. 

The time is displayed on a subdial at 12 o’clock, and the ring-shaped calendar displays at 3, 6, and 9 o’clock seem to float between the balance wheel and the rest of the movement. The power reserve and leap year indicators are located at 4:30 and 7:30, respectively. The watch crystal and case back are made of sapphire crystal, which offers an unobstructed view of the masterful movement at work.  

The Legacy Machine Perpetual Palladium will go on sale on September 14, 2021. 

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About the Author

René Herold

My name is René Herold, and I first discovered Chrono24 in a job listing. Admittedly, I didn't really care about watches before coming to Chrono24. However, after a few …

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