How does a perpetual calendar know about leap years?

A four-year cam wheel — typically driven once per year by the calendar mechanism — tracks the leap-year cycle. The cam has three high points and one low; the low point engages on 28 February of leap years to allow the date to advance to 29 February before rolling over to 1 March. In all other years the date rolls from 28 February directly to 1 March. The mechanism is mechanically simple but requires precise timing during assembly.

What happens in 2100?

On 28 February 2100, every conventional perpetual calendar will incorrectly advance to 29 February (because the four-year cam doesn't know about the Gregorian century rule that excludes years divisible by 100 but not 400). The watch will then require a single manual adjustment to skip from 28 February to 1 March. Some 'secular calendar' watches (a much rarer complication) account for the century rule and require no adjustment until 2400.

Can I wind a perpetual calendar without damaging it?

Generally yes — but never advance the calendar between roughly 9pm and 3am, when the calendar mechanism is engaged with the date wheel. Forcing the date forward during that window can break delicate components. If your perpetual calendar has stopped, advance the time manually to 6am and then perform any calendar adjustments needed.

Is a perpetual calendar a sound investment?

Iconic perpetual calendar references from Patek, AP and VC have appreciated meaningfully over the long term — these are halo complications produced in low numbers by the most prestigious houses. They are also expensive to service (figure $2,000+ for a Patek perpetual service) and require specialist watchmakers. We treat perpetual calendars as collectables to wear, not as financial instruments.

Style · Luxury Watches

Perpetual Calendar Watches for Sale

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A perpetual calendar is the most elegant complication in horology: the watch knows the date, day, month, and leap year, and adjusts automatically for months of varying length — including the leap-year exception. Set correctly, a perpetual calendar requires no manual date adjustment until 28 February 2100, when the Gregorian calendar century rule will require a correction (because 2100 is divisible by 100 but not by 400, so it will not be a leap year). The Patek Philippe Perpetual Calendar references — 5327G in white gold, 5320G with retro-style Arabic numerals, 5236P-001 with in-line calendar — are the modern standard for the complication. The AP Royal Oak Perpetual Calendar 26574 brings the perpetual calendar into the integrated-bracelet sport-watch idiom. The Vacheron Constantin Traditionnelle Perpetual Calendar in white gold or platinum is the connoisseur's choice. Perpetual calendar watches require careful service — the calendar wheels and the leap-year mechanism must be precisely set when reassembled — and our global network is the rational route to ownership for almost every reference.