“Complication.” It’s a funny word used in the world of watches, but all it means is as any functionality – besides hours, minutes and seconds – on a timepiece. They’re called such because the more complications on a time piece, the more, well, complicated it is to make. In our digital age, many of these complications serve little actual use, and are instead appreciated for the engineering expertise required to properly execute them in a timepiece measured in the millimeters.

TIME COMPLICATIONS

GMT

In 1952, the British de Haviland Comet became the first commercial jet airliner in service. With the dawn of the commercial Jet Age, Pam Am approached Rolex about creating a watch specifically for its world-travelling pilots. Two years later, the world was introduced to the Rolex GMT-Master, a watch that allowed its wearer to track two time zones. The watch simply added an additional hour hand that tracked to the now iconic red-and-blue Pepsi 24-hour bezel: blue for nighttime hours, red for daytime hours. It’s called a GMT watch because pilots would set this additional hour hand to GMT time so they could all communicate off a base time. Of course, now wearers will set the secondary hour hand to their home, using the watches main indication for the time zone they are travelling in. While Rolex was the first, many brands now offer compelling GMT watches great for travellers who want a durable, water-resistant watch that harkens back to the early days of aviation.

WORLD TIMER

A world timer watch is something like a GMT watch on steroids. It has 24 markers on it, allowing its wearer to take a quick glance and immediately know the time in all 24 time zones, typically by placing the name of a large city at each marker. Often, these watches have beautifully decorated maps at the center of the dial, making sure everyone in the room knows that the wearer is indeed an important, globetrotting businessperson. Swiss watchmaker Louis Cottier is credited with creating the first mechanism to display all 24 time zones on a dial, while Patek Phillipe is credited with creating the first world time wristwatch (before Rolex created the GMT in the 1950s).

REPEATER

A repeater is a complication that chimes the hours, and typically minutes, at the press of a button on the watch. Minute repeaters will chime the hours, quarter hours, and minutes in different tones. While they originally had utility, helping the visually impaired, or helping to tell time in the dark before artificial illumination or luminescence became widespread, these watches are now mainly collectors’ items.

STRIKING WATCHES

Striking clocks, unlike repeaters, do not chime on demand, but at regular intervals - usually at each hour or each quarter hour. Think Big Ben, but on your wrist. No, you can’t turn them off. While it’s a completely useless complication now, it is an interesting horological invention, and Wikipedia has a nice illustration of the mechanism used (below). Essentially, a release lever (L, below) holds up a rack (M) when the clock is not striking. There is a projection on the minute rotator (not shown), which rotates once per hour. This projection lifts the release lever, allowing the rack to fall until it rests on the snail (N), which determines how far the rack falls, and thus controls the number of strikes. At the hour, the striking gear train (G, H, K) lifts the hammer (F), which rings the gong (E). The gear wheel (H) makes one revolution per strike, while a small pin (S) lifts the rack by one tooth each ring, until the rack reaches its original position and the gong has been struck the requisite number of times.

DATE AND DAY-DATE

These complications are pretty self explanatory. When a date wheel is added to the movement, it allows for the watch to display the date. The best movements have quick-change dates that change in a split second. Sometimes, the color of the numbers alternates between red and black, called a “casino” date display. In a slightly different execution, some watches display the date with a date hand or pointer, which indicates the date by pointing to the corresponding number on the periphery of the dial.

A day-date complication simply adds the day of the week to this date wheel. Purists often complain about date windows, saying they take away from the symmetry of a dial, have little functionality, or worse. But, the best executed ones add an interest to the design that a time-only watch may be lacking. Sometimes, the date will be displayed in two separate windows (see right), adding another complication to this otherwise mundane function.

TIMING COMPLICATIONS

CHRONOGRAPH

When we’re talking “timing complications”, we’re actually talking about the chronograph and its various incarnations. The chronograph is a favorite complication among collectors everywhere, whether its a Rolex Daytona, Omega Speedmaster, or “the first automatic chronograph,” Zenith’s El Primero. A chronograph is simply a stopwatch combined with the typical watch that tells time. On a typical chronograph (such as the El Primero, left), the large sweeping seconds hand in the middle of the dial acts as the stopwatch. One subdial (at 3 o’clock on this El Primero) will act as the stopwatch’s minute hand, letting you keep track of how many minutes have elapsed since you started the timer. Another subdial (at 6 o’clock, here), acts as the stopwatch’s hour hand, letting you keep time for hours. Finally, a third subdial acts as the watch’s usual seconds hand. Sometimes, a tachymeter is added to the periphery of the chronograph’s dial. This indicator allows the user to quickly see units per hour (e.g. kilometers or miles), instead of having to do a calculation.
The term “chronograph” comes from the Greek for “time writing,” and this is indeed how early chronographs worked, as a small pen would attach to an index and mark how much time had elapsed. The first modern chronograph was invented in 1816, but was only developed for use alongside astronomical equipment.

In the early 1900s, the Breitlings added pushers to the chronograp at 2 o’clock (stop) and 4 o’clock (reset), adding additional functionality to what, by then, had already become an extremely popular complication. This further cemented Breitling’s reputation as the brand for aviators, and it soon leveraged its innovations by creating the Navitimer, the quientessential pilot’s watch.

Since then, chronographs have become a favorite among watch enthusiasts, often taking their place alongside historical moments or figures. Astronauts wore their Omega Speedmasters to the moon; Jack Swigert even used his to time a 14-second fuel burn aboard Apollo 13, the exact time needed to ensure the spacecraft was perfectly aligned for re-entry to Earth’s atmosphere. Heuer had its Carreras and Monacos (the later made famous by Steve McQueen). Paul Newman famously sported his Rolex Daytona (a certain dial variation now bearing his name).

FLYBACK CHRONOGRAPH

A flyback chronograph allows its user to reset the stopwatch function’s seconds hand of the watch without first stopping it. This not only allows the user to measure events in rapid succession, but also allows for the measuring of intervals. For example, laps in a race can be timed with a simple press of the flyback pusher, while the aggregate time of the race is still being kept as well.

SPLIT SECOND CHRONOGRAPH

The split-seconds chronograph is a more complex chronograph that has two central sweeping hands, allowing for the timing of two intervals that start at the same instant. This is referred to as rattrapante in French, and is widely considered the most complicated of the chronograph complications. Like so many complications, Patek Phillipe brought the first split seconds chronograph in a wristwatch to market, in 1923.

ASTRONOMICAL COMPLICATIONS

MOON PHASE

A moon phase watch does just that: shows you the phase of the moon as it appears in the night sky. It’s displayed using an aperture on the dial that tracks the movement of our actual lunar pal, rotating around the Earth every 29.5 days. These displays are often ornately decorated, a this complication has more aesthetic than utilitarian appeal to us now. When a new moon is turning into a full moon, it’s waxing; as it reverts back to a new moon (perfectly aligned with the sun on the same side of Earth, such that we can’t see the moon in the night sky), it’s waning. It’s a beautiful complication, and while it has little utility, neither do wristwatches; it’s a great way to feel connected to our less developed ancestors, whose lives more completely revolved around lunar cycles.

Triple Calendar

A triple calendar complication simply adds the month to a typical day-date display.

ANNUAL CALENDAR

An annual calendar watch displays the day, date and month on its dial, all with minimal adjustment. The complication is also able to automatically adjust to 30- or 31-day months, thus the “annual” moniker. In theory, this watch need only be adjusted once a year, at the end of February.

PERPETUAL CALENDAR

The perpetual calendar is even more complicated than the annual calendar. It displays the same information as the annual calendar, but does not even require adjustment in February. It knows the year in relation to the next leap year (i.e. it keeps track of years in four-year cycles), so is able to automatically account for leap years. It rarely needs to be adjusted - because of the oddity of leap years, a perpetual calendar will need to be adjusted next in 2100.

Equation of Time

An equation of time display shows the difference between true solar time and “mean” solar time. For convenience, humans have defined the a day as 24 hours. But because Earth’s orbit isn’t quite round and because it sits on 23-degree axis, any particular day may be slightly more or less than this 24-hour average. This is typically displayed on a watch by indicating the difference (plus/minus minutes) between true solar time and mean solar time. Because of the astronomical knowledge it takes to execute this complication, it’s often combined with other astronomical or calendar complications.

Technical Complications

Tourbillon

A tourbillon (French for “whirlwind”) is a complication designed to counter the effects of gravity, by placing the watch’s escapement and balance wheel in a rotating cage. It was patented by watchmaker Abraham-Louis Breguet in 1801. A tourbillon continuously rotates the contained balance wheel and escapement, averaging out positional errors to, in theory, achieve more accurate timekeeping. Today, it’s primarily a complication to display to others how rich you are. Because of advancements in engineering and design, tourbillons are not needed to create a more accurate movement; in fact, there is often debate as to whether they ever actually served this purpose. Either way, they’re typically considered one of the most complex achievements in haute horology.

Power Reserve

A power reserve indicator simply measures the amount of power remaining in the watch, based on the tension left in the mainspring. It’s a useful complication, often placed on the dial, but sometimes placed on the back of a movement, where it can be seen through the sapphire case back.