What does “Complication” mean?

A complication is any function a watch performs beyond showing the hours, minutes and seconds. Common complications include the date, day-date, chronograph, GMT or second time zone, moon phase, annual and perpetual calendars, power reserve indicator, alarm and minute repeater, and the tourbillon is usually counted among them too.

Complications add engineering, cost and usually value, and the most complex, such as perpetual calendars and minute repeaters, sit at the top of fine watchmaking. They also add things to check: every function should work correctly, and some need careful handling, for example not adjusting a calendar during the hours when its mechanism is engaged. Service costs rise with complexity. In listings, name each complication and confirm it works, since a careful buyer will test them all.

Example: 'Annual calendar and moon phase, all functions working, serviced 2023.'