A complication is any function on a watch other than the display of time. Complication may include displays of the date, chronograph functions, tachymeter to the extreme articulating functions of a tourbillon.
- The simplest complication on a watch is the date display.
- Date Window
- This window is also known as an aperture. On some watches the color of the numbers alternate between red and black, this is called "Casino" date display.
- Big Date
- Is a significantly larger view of the date and is more legible than the traditional date window. Dependent upon the watch brand, there may be two date windows: the left aperture displaying 0-3, and the right aperture displaying 0-9.
- Date Wheel
- Is usually a center hand with an arrow or crescent, pointing to the date along the outside periphery, also known as a chapter of the dial, often referred to as a 'Bankers' date.
- Subsidiary Dial
- Displays the date on a small sub-dial, is often used in combination with other complications.
- This includes the day of the week to the date complication. Two common styles are:
- Classic Day-Date Dial
- Side by Side Day-Date Dial
- Triple Calendar
- Also referred to as 'Complete Calendar', is a further elaboration of the date display with the month of the year.
- Perpetual Calendar
- Is by far the most complex type of calendar feature that exists on a watch. It accurately displays the date, day, month, and year, and even takes into account the leap year. However, it will need correction in 2100 when the leap year will be ignored.
- Annual Calendar
- An intermediary complication having both perpetual calendar and triple calendar complications. However, it does not take leap years into account and will continue to run through February 31st before advancing to the first of March.
A chronograph watch has a stopwatch built into the movement.
Types of Chronographs:
- Mono-Poussier (One-Button Chronograph
- All chronographs were originally Mono-Poussiers; The one-button chronograph is incapable of measuring interrupted time spans, unlike the two button chronograph.
- Retour-en-Vol (Flyback Chronograph)
- The Flyback chronograph was designed with pilots in mind. When a second button is pushed, while the chronograph is running, all the counters reset and immediately start again from zero.
- Rattrapante (Split-Second Chronograph)
- Chronograph with three pushers on the case and two second-hands on the chronograph, one on top of the other.
Dual Time Zone (Travel) Complications
- Dual Movement
- Watches with two separate movements each independently operating from its own power source and capable of being set independently (more a feature than a complication).
- Dual Time
- Dual Time watches have two time displays that are powered by a single movement.
- GMT (Greenwich Mean Time)
- A watch that displays two or more time zones.
- GMT (Greenwich Mean Time) with Independent Hour Hand
- This watch is an expanded version of original GMT watch. It has an independent 24 hour hand as opposed to the 12 hour hand on the GMT watch.
- (Greenwich Mean Time) with Fixed Hour Hand
- It is an additional hour hand that makes one revolution in around the dial in a 24-hour period. It is considered to be a pilot’s watch. It is was first introduced by Rolex in the 1950's.
- World Time Zone
- It is a watch with an intricate set of time zone complications with features like a rotating inner bezel with 24-hour display and an outer bezel that lists major cities in 24 time zones.
Tachymeter, Tourbillon and Other Complications
- Tachymeter (Tachometer) Complication
- The tachymeter complication is a feature found near the watch bezel with an inscribed scale, usually on the inside rim of the dial. It is used to measure speed over a specified distance. This complication is typically found on chronograph watches.
- The Tourbillon
- Is a complication that was originally developed to eliminate the negative effects of gravity, thereby improving the accuracy of timekeeping. It was developed in 1795 by Abraham-Louis Breguet. It is a complication primarily found on luxury watches - as it extremely laborious to construct.
- Moonphase Complication
- Is an aesthetic complication that displays the current phase of the moon through an aperture. It displays full, half, quarter, or new moon phases.
- Power Reserve Indicator
- Measures the amount of remaining power stored in the watch, which is displayed by the tension on the mainspring. A watch’s power reserve can vary from 7 to 10 days, depending on brand and/or model. This complication is found exclusively in mechanical watches.
- Jump Hour
- Is a complication that displays the hour through an aperture and jumps to display the hour thereafter every 60 minutes.
- Minute Repeater
- It is a movement, typically found in mechanical watches, that chimes at different time intervals when a lever is pressed. This complication was popular in watches made during the 18th and 19th centuries. It is generally produced as a limited edition watch exclusively for collectors desiring a one-of-a-kind timepiece.