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The Encyclopedia of Horology

Complication · Calendar & astronomy

Annual Calendar

Partially verified

A calendar needing correction only once a year.

Definition

A calendar needing correction only once a year.

Historical origin

A twentieth-century refinement between simple and perpetual calendars, offering most of the convenience at much lower complexity.

How it works

Cam and lever work recognises thirty- and thirty-one-day months and skips the extra day automatically.

February is not recognised, so one manual correction a year is required.

Pocket watch context

A modern concept rather than a pocket-watch one.

Wristwatch context

A popular practical calendar complication in modern wristwatches.

Identification

  • Day, date and month displays with no leap-year indication

Servicing notes

This is specialist work. Levers, springs and cam profiles in complicated work are calibre-specific, and incorrect reassembly commonly damages parts that cannot be bought. Refer the movement to a watchmaker experienced with this mechanism.

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.