Complications, in a mechanical watch, are mechanical disposals added to the basic movement, needed to indicate additional information to that of the hour. Complications are always connected to time flowing: to make some examples:

• Chronographs, for the measurement of short time intervals, such as racing performances;
• Calendars, from the simple ones, with the indication of the date, to annual or perpetual calendars, able to distinguishing among different lengths of months or among regular and leap years;
• GMT and Worldtime, to indicate two or more time zones,
• Astronomical indications, such as the moon phases and the more complex sky map or equation of time.

In this field, it is important to recognize also a complication that we usually consider as a basic feature of a watch: the central second hand.

Continues

Aquanaut ref. 5167A Patek Philippe, in acciaio e cinturino in tropical, equipaggiato con il Calibro 324 S C (con calendario e secondi al centro)

Il Chronomètre à resonnance di F.P.Journe. Il principio fisico della risonanza allinea il moto dei due bilancieri, riducendo sensibilmente gli errori di marcia.

Master Grande Tradition Tourbillon Cylindrique à Quantième Perpétuel, della collezione Jubilée di Jaeger-LeCoultre. Questo calendario perpetuo è equipaggiato con un calibro dotato di tourbillon volante che, per la prima volta, è abbinato ad una molla cilindrica.

Il cronografo El Primero di Zenith. Con una velocità di 10 alternanze al secondo (ovvero 5 oscillazioni /sec. pari 5 Hz), permette la leggibilità anche del decimo di secondo nei tempi cronografici.

Patrimony Contemporaine con calendario a doppia indicazione retrograda del giorno e della data.

The visual indication of the time flow, through the second hand placed in an off-centered subdial, should always be included in a watch, and cannot be considered as an additional complication (except in ultrathin models, where the second hand is eliminated so as to reduce the thickness of the movement).

However, when the second hand is placed in the centre of the dial, coaxial with the hour and minute hands, this can be defined as a complication: traditional mechanical of watches places in an off-centred position the second wheel, meaning that an additional wheel train is needed to transmit the movement to the centred second hand.