A perpetual calendar is one of the most classic complications for a watch and one of the most difficult to maintain, according to Maximilian Büsser, founder of luxury watch brand MB&F.
“I call perpetual calendars boomerang watches because they come back for repair so often,” he says. “The mechanisms jam, block, break or jump days when they shouldn't.”
So when Irish watchmaker, Stephen McDonnell, came to Büsser with a new way to design a perpetual calendar, he was all ears. The resulting timepiece, Legacy Machine Perpetual, solves several problems inherent in traditional perpetual calendars while creating a new aesthetic for the complication, according to its makers.
Traditional perpetual calendars use a grand levier (lever) system, which assumes that, by default, all months have 31 days, Büsser says. Any manipulation or adjustment of the date during the monthly changeover can result in damage to the mechanism. The dates can also jump or skip during changeover, “negating the whole point of the perpetual calendar, which is not requiring adjustment for years,” Büsser says.
The 581-component caliber includes a patent-pending “mechanical processor” consisting of a series of superimposed disks. It takes the default number of days in the month at 28 (because, all months have at least 28 days) and then adds the extra days as required by each individual month. This ensures that each month has exactly the right number of days.
“There is no ‘skipping over’ redundant days, so there is no possibility of the date jumping incorrectly,” Büsser says.
The mechanical processor also enables quick-setting of the year so that it displays correctly in the four-year leap year cycle, whereas traditional perpetual calendar mechanisms may require the user to scroll through up to 47 months to arrive at the right month and year. And there’s an inbuilt safety feature that disconnects the quickset pushers during the date changeover, eliminating any risk of damage while the date is changing.
“The end here was to create a calendar which is foolproof,” McDonnell says. “You can press the correctors whenever you like. You can manipulate anyway you like. But whatever you do, you’re not going to break anything; you’re not going to damage anything.”
Replacing the big level system with MB&F’s mechanical processor enables the centre of the complication to be used, “thereby saving space and allowing design freedom as the full dial is no longer necessary,” according to the Geneva-based watchmaker.
With this new system, all of the indications of the perpetual calendar mechanism are placed on top of the movement’s main plate using skeletonized subdials, making the calendar easier to read while providing a new aesthetic.
“There’s no real difference between the display and the mechanisms,” McDonnell says. “The dials now appear to completely float in midair.”
Legacy Machine Perpetual launches with a limited edition of 25 pieces in 18k red gold and 25 pieces in platinum 950.
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