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The Encyclopedia of Horology

Complication · Calendar & astronomy

Secular Perpetual Calendar

Partially verified

A calendar complication that accounts for the century-year exceptions in the Gregorian calendar.

Definition

A calendar complication that accounts for the century-year exceptions in the Gregorian calendar.

Historical origin

Developed in the nineteenth century for high-grade clocks and later adapted to pocket watches; extremely rare due to the 400-year cycle.

How it works

Uses a specialized wheel that rotates once every 400 years.

Correctly skips the leap year in years like 1800, 1900, and 2100, which are normally leap years but for the Gregorian secular rule.

Pocket watch context

Found only in the most prestigious grand complications from makers like Patek Philippe.

Wristwatch context

An ultra-high complication, showcased in watches like the Patek Philippe Calibre 89 and recent Vacheron Constantin masterpieces.

Identification

  • Indicator for the century or a 400-year wheel visible
  • Manual adjustment not required for 400 years

Servicing notes

Extremely complex; requires a specialist with experience in secular gearing.

General guidance only. Complicated mechanisms should be assessed and serviced by a qualified watchmaker or clockmaker specialist, not adjusted at home.

Diagram

date ring, thirty-one positionsdate aperturedriving wheel and jumper
Schematic: calendar work under the dial. An outline schematic drawn to show the arrangement of the parts discussed here. It is not a dimensioned working drawing and does not depict a particular maker's calibre.

Sources & references

  1. de Carle, D., Watch and Clock Encyclopedia
  2. Britten, F. J., Old Clocks and Watches and Their Makers
  3. Horological Journal (British Horological Institute), technical articles

Where sources disagree, the disagreement is stated rather than resolved silently.