Watch Complications Guide. The difference between a "complication" and a "function."

Complications are best understood as complicated mechanical functions beyond regular time-telling, that display a high degree of skill and craftsmanship. Complications are by definition mechanical so, for example, a quartz watch with a battery could have multiple functions, but they would not be called complications. Luxury watchmakers pride themselves on their complications as a way to show off their ingenuity. There is strong competition among the world’s top brands to see who can get more 'complicated.'

The most popular complication

What is the most common complication? That is probably the moon phase display, usually an elegant illustrated dial, especially suited to dress watches.

How does it work? Typically an aperture in the face shows a disc with two moons on it. The disc rotates every 29.5 days, driven by a toothed gear that is advanced by a mechanical finger one notch every 24 hours. The display shows the waxing or waning of the moon. A 135-toothed moon phase will remain accurate for 122 years!

Beyond the moon phase

For the true collector, the array of information that can be engineered into a wristwatch goes way beyond the moon. Makers have accomplished complications that show the date accurately (including leap years) through the next century. Some can chime on the hour and quarter hour, like a grandfather clock on your wrist. There are complication stopwatches accurate to 1/10 of a second, and one that shows the precise solar length of the day (Only four days a year are exactly 24 hours long. The rest are an approximation. But you knew that, right?)

A guide to watch complications

Here are some of the most popular complications. Remember, these are all mechanical accomplishments – no computer chips were harmed in the making of these wonders:
Alarm Watch: Complete with chime. More elegant than your bedside clock by a factor of a gazillion.
Annual Calendar: These automatically adjust between 30 days and 31 days of the month all year. The only caveat: it has to be manually adjusted for February.
Automatic Watch: This popular feature winds itself by the movement of the wearer. It usually manages this with a rotating disc.
Chronograph: This sporty option is a timer showing seconds and sometimes increments, minutes and hours. Learn more about the chronograph in this post.
Double Chronograph or Rattrapante: This advanced complication is a split-second timer or lap timer. It customarily has two hands to show the split time.
Dual (or Multiple) Time Zone: For world travelers, dual or multiple time zone displays can use either two hour hands or one or more sub dials. Multiple time zone watches often also have 24 hour indicators on the bezel.
Equation of Time: “Apparent Solar Days” are the observable length of the days, which can vary by as much as 16 minutes shorter or longer than 24 hours depending on the earth’s position relative to the sun (during the solstices and equinoxes). This complication indicates the minutes to be added or subtracted in order to equate the exact length of the day.
Flyback Chronograph: A sophisticated time-saver, this complication can instantly reset the chronograph while it is running, without stopping the motion, resetting and then starting again.
GMT: Displays Greenwich Mean Time in an additional subdial. Can also serve as a dual time zone watch.
Leap Year: Usually seen in watches with a perpetual calendar, the leap year complication numbers the years as 1, 2, 3 and 4 - with 4 indicating a leap year.
Minute Repeater: One of the earliest and most useful complications before the age of electric light. A watch with this complication chimes the hours, quarter hours, and minutes with the push of a button or a lever. Inside, small hammers strike tiny gongs to create graduated tones for the minutes, hours and quarter hours. Once highly valued by sailors and soldiers who needed accurate timing but couldn’t see their watches in the dark.
Moonphase: Displays the phases of the moon in a subdial.
Perpetual Calendar: Differs from an annual calendar, as it adjusts automatically for February and leap years without needing to be reset, usually until 2100.
Power Reserve Indicator: Useful for automatic watches, this complication indicates how much longer the watch will run before stopping. Obviously useful and also a lot of fun to watch as the movement of your wrist winds the watch.
Sector Dial vs. Cross Hair Dial: A sector dial features markers indicate hours, minutes or both. Believed to be popular with military officers because markings correspond to map directions, i.e. “incoming at 2 o’clock.”  A cross hair dial centers on the dial and extends from 12, 9, 6 and 3.
Tourbillon: Mechanical watches are less accurate because as the wearer’s wrist moves, gravity exerts force on the parts. The tourbillon is a small “cage” for the balance, hairspring and escapement, designed to increase accuracy by rotating within the watch housing. They are an indication of great watchmaking skill.
World Time: A complication that simultaneously displays the time in multiple time zones. Many use the name of a major city to indicate the zone.



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