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The Encyclopedia of Horology

France / Switzerland / England · Mechanisms in production by the mid-19th century; refined mainsprings of the type through the 20th century

Perpetual Calendar Watch Mechanism

Needs research

One of the 'grand complications' prized in fine watchmaking, and a useful teaching example of mechanical calendar logic.

A perpetual calendar mechanism tracks the varying month lengths and leap years mechanically, usually via a stack of cams reading a four-year (or longer) cycle, so the date, day, month and moon phase (where fitted) advance correctly without manual correction except at the turn of a non-leap century.

Unlike the escapement or overcoil, no single named inventor and confirmed patent number for the perpetual calendar complication as a whole is well established in the mainstream literature available to this project; claims naming a single inventor should be treated cautiously.

How to verify this yourself

This entry is marked needs-research for a specific founding patent. Consult the Patek Philippe Museum's published history and INPI/Swiss IPI archives directly rather than relying on unsourced marketing timelines before citing a first inventor or patent number.

Manufacturers known to have used it

  • Patek Philippe
  • Audemars Piguet
  • many haute horlogerie manufacturers

Sources & references

  1. Patek Philippe Museum, published company history
  2. No single verified founding patent identified in project research to date — flagged for further archival work

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