The 5 Most Common Watch Complications And What They Do

The term "complication" in watchmaking is not about something that went wrong with it - it just refers to any function beyond the basic display of hours, minutes, and seconds. These features are the result of centuries of innovation, combining precision engineering with artistic design.

Sure, they may seem gimmicky to a minimalist watch fan who just wants to know what time it is right now, but each mechanism serves a specific purpose and adds functionality while also adding depth to a watch’s design. In this article, we’ll go through the five most common watch complications, exploring their mechanics, and practical applications that will hopefully allow you to appreciate watches even more.

Day/Date Display

The day/date display is one of the most practical and widely used watch complications that shows the day of the week and the date of the month. Typically located at the 3 o’clock position on the dial, it shows the current date through a small window cutout. More advanced versions, such as the "big date" or "pointer date," display the date in larger numerals or with a dedicated hand for improved readability, while others add a “cyclops” (or magnifying glass). Mechanically, the date complication is driven by a gear that advances once every 24 hours, synchronized with the watch’s timekeeping function. Some watches also include a quick-set feature, allowing the wearer to adjust the date independently of the time.

Additional trivia: if the movement has a day or date wheel function, but the dial does not have a day/date window, the complication is referred to as a “Ghost Day/Date.” While a minor flaw (if you can even call it that), it does bother some watchmakers knowing that the complication is being covered up and rendered useless.

GMT/Dual Time Zone

The GMT complication, also known as a dual time zone function, is a sought-after feature for frequent travelers and professionals working with global companies. It allows the wearer to track a second time zone simultaneously, often through an additional hand or a rotating bezel marked with 24-hour increments. Originally developed for pilots and frequent flyers, the GMT complication gained fame with the introduction of the Rolex GMT-Master in the 1950s. Modern variations include world time complications, which display multiple time zones at once, often through a city ring and a 24-hour disc. 

There are two main types of GMT movements: "office/caller GMT" and "true GMT." An office GMT, adjusts the local time by moving the main hour hand in one-hour increments, while the GMT hand remains fixed. This is the mechanism for the Seiko 4R34/NH34. A true GMT, typically seen in higher-end watch models, allows the GMT hand to be set independently, making it easier to track a second time zone without disrupting the local time.

Chronograph

Source: @harry_apriliandi on IG

The chronograph encompasses a wide range of complications, but is mainly used to refer to the stopwatch function. It allows the wearer to measure elapsed time with precision, using pushers on the crown-side of the case to start, stop, and reset the timer. The chronograph typically features sub-dials that display seconds, minutes, and sometimes even hours depending on the model, which admittedly can sometimes lead to a “busy” dial. 

One of its most notable variations is the tachymeter scale, which allows for the calculation of speed based on time and distance. There are also flyback and split-second chronographs that cater to specialized needs like aviation or competitive sports.

Moon Phase

Source: @teddybaldassare on IG

The moon phase complication is a poetic and visually arresting feature that tracks the lunar cycle, displaying the current phase of the moon on the watch dial. This makes it a favorite for luxury dress watches. This complication is driven by a mechanism that replicates the moon’s 29.5-day orbit around the Earth, often depicted through an aperture with a rotating disc. 

Historically, moon phase indicators were used by sailors and farmers to track tides and planting cycles, but today, they are primarily appreciated for their added flair. High-end watches may include highly detailed lunar discs, sometimes even crafted from precious metals. While not as practical as other complications, the moon phase adds a layer of artistry and sophistication to a timepiece, making it a favorite among collectors and those who value the blend of science and art in horology.

Power Reserve Indicator

Source: Worn and Wound

The power reserve indicator is a practical yet often underappreciated complication that shows the remaining energy in a mechanical watch’s mainspring. This feature is especially useful for manual-winding and automatic watches, as it alerts the wearer when the watch needs to be wound or worn to maintain accuracy. The indicator is typically displayed as a scale or sub-dial, ranging from “full” to “empty,” and is driven by a mechanism that measures the tension of the mainspring. 

While its primary purpose is functional, the power reserve indicator also adds a technical and visual element to the dial, appealing to those who appreciate the inner workings of their timepiece.

Wrap Up

Complications turn simple timekeeping machines into something more functional, while also showing the culmination of many years of horological progress. They can be quite practical, with functions that you’ll use everyday, or special nice-to-haves that will let you appreciate the uniqueness of your watch. And take note that these are not all of the complications available - just some of the most common. There are also sunset and sunrise calculators, perpetual calendars, and even death predictors! But those will be topics for another article.

Which of these complications make an appearance in your watch collection? Have you modded a custom watch with these before? Let us know in the comments below!