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The Encyclopedia of Horology

Pocket watches · Complication

Calendar Pocket Watches

Partially verified

Watches displaying the date, and often the day and month, in addition to the time, ranging from simple date apertures to full perpetual calendars.

Mechanism

A calendar wheel advanced once per 24 hours by a jumper acting on the motion works drives the date display; perpetual calendars add a program wheel that reads the length of each month over a four-year cycle.

Typical characteristics

  • Date hand, aperture or subsidiary dial
  • Additional day-of-week and month indications on more complex examples
  • Perpetual mechanisms that account for varying month lengths and leap years

Identification characteristics

  • Extra dial furniture for date, day or month
  • Correction pushers set into the case band on perpetual examples

Collector significance

A widely produced complication ranging from simple and robust to among the most complex mechanisms made.

Known variations

  • Simple date
  • Triple calendar (day, date, month)
  • Perpetual calendar
  • Annual calendar

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. General horological surveys

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