Perpetual calendar
A complication that displays the date and accounts for all calendar irregularities — varying month lengths, leap years — automatically. A correctly set perpetual calendar requires no manual correction until the year 2100.
At a glance
- Indications
- day, date, month, leap year
- Common addition
- moonphase
- Leap-year cam
- four years
- Correction required
- 2100 (standard) or 2400 (secular)
- Pushers
- dedicated quick-set on case flank
- Standstill before desync
- up to 24 hours
- First Patek wristwatch with perpetual calendar
- 97975 (1925)
- Iconic vintage reference
- Patek Philippe 1518 (1941)
- Secular references
- Patek 5208P, Greubel Forsey QP à Équation
A perpetual calendar is a complication that displays the date and accounts for all calendar irregularities — months of 30 or 31 days, February with 28 or 29, leap years — automatically. A correctly set perpetual calendar requires no manual correction until the year 2100.
What it displays
Most perpetual calendars display:
- Day of week
- Date (1–31)
- Month
- Year — or a leap-year indicator on a sub-dial
Higher-end versions add:
- Moonphase
- Equation of time
- Solar and sidereal time
- Hijri-calendar correspondence
How it knows the leap year
A four-year cam tracks the leap-year cycle. February shortens to 28 days in normal years and 29 in leap years automatically. The Gregorian exception — years divisible by 100 are not leap years, except those also divisible by 400 — is why most perpetual calendars need a manual correction in 2100: 2100 is divisible by 100 but not 400.
Secular perpetual calendars
A handful of secular perpetual calendars (Patek Philippe 5208P, Greubel Forsey QP à Équation, Jaeger-LeCoultre Master Hybris Mechanica) account for the 100-year rule mechanically. They run uncorrected until the year 2400.
Setting and care
A perpetual calendar must keep running. If it stops for more than 24 hours, the displays fall out of sync and must be reset via dedicated pushers — often a workshop matter. Some makers integrate a quick-set system that simplifies the procedure; others require manual advance through every missed day.
At our atelier in Munich setting a perpetual calendar — and the service that typically follows — is a standard procedure.
Notable perpetual calendars
Patek Philippe 5320G, 5230G and the vintage reference 1518; Audemars Piguet Royal Oak Perpetual Calendar 26574; Vacheron Constantin Patrimony QP; A. Lange & Söhne 1815 Annual Calendar; IWC Da Vinci Perpetual. The complication is often combined with a chronograph — a configuration Patek Philippe has shaped since the 1518 of 1941.
Frequently asked
- An annual calendar only accounts for months of 30 or 31 days automatically. February must be set manually once a year, as must every leap-year change. A perpetual calendar handles both — no intervention until 2100. Patek Philippe defined the annual calendar in 1996 as a deliberately simpler construction; the gap in price and service cost between the two is substantial.