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Some watch complications have names that make them sound mysterious. Others are much easier to grasp. The moon phase clearly belongs in the second group. Poetic, charming, elegant… Browse any watch enthusiast forum, and you'll find plenty of ways to describe it.
Want to learn more about this dreamy complication? You're in the right place!
In watchmaking, a “moonphase” (also written “ Moonphase ,” “ Moon Phase ,” or “ Moon-Phase ”) is a complication that displays the Moon's current phase. Before we get into the details, though, let's cover one important point…
Unlike the Gregorian calendar we use every day, which is based on the solar cycle, the Moon's phases follow the lunar cycle. It lasts exactly 29.53 days, or, to spare you the math, 29 full days, 12 hours, 44 minutes, and 2.9 seconds. Now that's precise!
The Moon's eight phases (Source: Kronos 360)
Despite what you might think, the Moon's phases aren't hard to understand. They simply describe how the Moon appears to us from Earth. What we see depends largely on how much of the Moon is illuminated.
In watchmaking, the Moon's phases are generally shown through an “ aperture ” or “ date window .” This opening in the dial is often crescent-shaped. Through it, you can see a rotating disk bearing an image of the Moon, sometimes accompanied by stars.
Position of the moonphase aperture on a Herbelin watch
A fun detail: depending on the watch, the Moon might appear as a simple, minimalist circle or have a face complete with eyes, a nose, and a mouth… This once-popular human-like depiction still gives the complication a special charm today.
With that in mind, a moonphase watch is, by definition, a watch that displays the Moon's current phase. Some watches go further, adding information such as the Moon's age or the precise time when the next full moon will be visible.
Don't be fooled, though… Some watches on the market look remarkably like moonphase watches but aren't! These timepieces actually have a day-night complication, which uses a small window to show the progression of the day.
Moonphase watch vs. watch with a day-night complication
As you can see, some of these watches look strikingly similar! That's why it pays to do your research, especially if you're planning to buy a true moonphase watch.
Finally, on French watch forums, enthusiasts often use the abbreviation “ PDL ” for the “Phase De Lune,” or moonphase, complication. Keep that in mind if you're searching for information online.
Now that you know what a moonphase watch is, let's explore the fascinating history of these timepieces, a story that began centuries ago…
If you've read our watch guides, you may have noticed… Watch complications of all kinds often appeared in early timekeeping instruments long before they made their way into wristwatches. Our ancestors were remarkably skilled!
The moonphase complication followed the same path. By the 17th century, it had appeared on small wall clocks as well as table clocks.
17th-century German moonphase clock (Source: Koller Auktionen)
Often built on a metal base, these clocks were then painted to suit the tastes of their time. Look at them today and one thing stands out… They were genuinely handcrafted, and their imperfections are part of their charm. Mass-produced clocks as we know them were still a long way off.
In the 17th century, watchmakers took the next step: miniaturizing the moonphase complication for use in pocket watches. Portable watches were all the rage at the time!
17th-Century Moon Phase Pocket Watch (Source: Bonhams)
That's right: at the time, they served much the same purpose as the wristwatches we wear in the 21st century, except these early watches were carried in a vest pocket. And so the first moonphase pocket watches were born!
The example you're looking at is a perfect illustration. It's remarkably comprehensive: besides showing the phases of the Moon, it displays the Moon's age and a range of other useful information. And it does all that with a 100% mechanical movement… Impressive, isn't it?
Want to learn how timepieces powered by tiny components and gears work? Take a look at our guide to mechanical and automatic watches!
One surprising detail about the watch pictured here: although its movement was made in the 17th century, its 44 mm-diameter case , crafted from gold-plated sterling silver , appears to have been made later… Engravings on its surface suggest it was produced in 1819 in London, England.
In the 18th century, moon phase complications began appearing on large clocks. They looked a lot like the clocks many of us remember from our grandparents' homes!
18th-century James Wilson moonphase clock (Source: Concept Art Gallery)
They were fairly large, made from quality hardwoods such as oak or mahogany, and fitted with a large aperture to display the current phase of the Moon.
These clocks came in all kinds of styles! Many originated in England, and the disks that displayed the Moon's phases were often so artfully decorated they resembled miniature paintings.
Moonphase disk from an antique mahogany clock, circa 1860 (Source: Pamono - Seller 5034)
It's hard not to admire the level of detail in these clocks! Handcrafted with exceptional skill, they were true works of art.
If you'd like to find one of these clocks, try websites specializing in antique decor or keep an eye on auctions. The style certainly won't appeal to everyone, but it has a distinctive look and embraces it fully!
Watches developed in the 19th century often displayed a perpetual calendar as well as the moonphase, adding another complication. Some even featured a minute repeater. In other words, these watches housed remarkably complex movements!
Patek Philippe moonphase pocket watch (Source: Bonhams)
In keeping with the tastes of the time, these watches often had cases made of 750/1000 yellow gold (18 karats). Most were made in Switzerland or England and carried no brand name on the dial. But major watchmakers, including Patek Philippe, Le Phare , and Gubelin , also offered such models, particularly in the late 19th century.
If you know the history of watchmaking, you know that the first wristwatches reached the market in the early 20th century . Then, in 1925 , Patek Philippe made headlines by announcing the first wristwatch with a moonphase complication! That watch was the Patek Philippe 97975 … A piece of rare elegance, it is also considered the first wristwatch to feature a perpetual calendar. Talk about two firsts in one!
Patek Philippe watch, reference 97975, 1925 (Source: Revolution Watch)
With this showcase of its watchmaking expertise, Patek Philippe made a bold statement in the 1920s. Its size makes it even more impressive: the watch measures just 34 mm in diameter! For its time, it packed a remarkable amount of technology into a small case.
In the first half of the 20th century, many brands offered watches with moonphase complications. They included major names such as Universal Genève, Jaeger-LeCoultre, Omega, Movado, Leonidas, and Angelus, as well as lesser-known makers such as Herala, Giroxa, Le Phare, and Henri Duvoisin.
Jaeger-LeCoultre Triple-Date Moonphase Watch, Circa 1950 (Source: Amsterdam Watch Company)
These watches often paired the moonphase display with one or more other complications, such as a chronograph or a triple calendar, adding to their complexity and prestige.
Rolex joined in too, introducing reference 8171 in 1949 . Produced for just three years, the watch was later nicknamed the “ Rolex Padellone ,” Italian for “frying pan,” by Italian collectors because of its 38 mm diameter. That was considered especially large in the late 1940s! Despite its limited production, it came in several versions, including yellow gold, rose gold, and stainless steel.
Rolex reference 8171, nicknamed “Padellone,” 1949 (Source: Rolex Magazine)
A yellow gold example offered by the renowned auction house Christie's in late 2008, estimated at between 150,000 and 250,000 Swiss francs, ultimately sold for 294,000 Swiss francs.
In the second half of the 20th century, several well-known watch brands added moonphase complications to their flagship models. Among them was Zenith , which introduced a feature-packed version of its famous El Primero called the “ Espada ” in the 1970s.
Zenith Espada reference 01.0040.418, circa 1970 (Source: Chrono24 - @Watches83)
Reference 01.0040.418 featured a moonphase complication, a triple calendar, and a chronograph. It was a remarkably versatile watch with several complications. In the mid-1980s, Omega introduced a redesigned version of its iconic Speedmaster with a moonphase display. A fitting addition to a watch worn by astronauts on the Moon!
Omega Speedmaster moonphase, reference ST 345.0809, 1985 (Source: Timeline Watch)
In the 1990s, Breitling introduced special versions of two of its iconic watches: the Chronomat and the Navitimer. Even the biggest names got in on the act!
These watches are relatively rare today, especially compared with the more conventional models the same brands sold at the time.
Breitling Chronomat moonphase, reference 81.950, circa 1990 (Source: Phigora)
The first quartz watches with moonphase complications also appeared on the market during this period. Seiko, Zenith, Cartier, and Jaeger-LeCoultre developed notable models whose designs reflected the trends of the time.
Moonphase watches may not be at the height of fashion today, but several brands still offer them. Browse online retailers and you'll find a moonphase watch for nearly any budget… Quartz models are, of course, more affordable than mechanical ones, but plenty of brands in this category are worth a closer look…
Quartz and automatic moonphase watches
Casio, Zeppelin, Citizen, Tissot, Herbelin, Mido, Baume et Mercier, Frédérique Constant, and Raymond Weil come from different backgrounds, but they all share a commitment to making quality watches!
A moon phase complication uses a rotating disc that advances once a day. Visible through a small opening in the watch dial, the disc always features two Moons. When the first disappears, the second comes into view and takes its place.
Note: If the disc had only one Moon on its upper half, you would see it for a while, then it would disappear for days... Adding a second Moon solves that problem. And, as you'll see, it wasn't the only challenge watchmakers faced!
It's worth noting that t he disk rotates with the help of several gears . You can't see them from the front of the watch, but they become visible when you look inside its movement.
Movement with a moonphase complication (Source: Siam Watch Club)
Earlier in this guide, we learned that a lunar cycle lasts exactly 29.53 days. That decidedly awkward number presented watchmakers with an obstacle: it kept them from achieving the ultimate precision they strive for…
Why? While a gear mechanism can be designed around one, two, 29, or even 29.5 increments, it can't have precisely 29.53… Watchmakers therefore settled on a moonphase disk mechanism based on 29 and a half increments. But what does this technical limitation mean for our beloved watches?
This creates a small margin of error, so moonphase watches aren't 100% accurate. Their displays drift by about one day every two and a half years. If you want yours to stay perfectly in sync with the Moon, you'll need to adjust the complication manually every two and a half years. A minor limitation, but one you'll probably agree is quite manageable!
If you're looking for an exceptionally accurate moonphase watch, a quartz model with a digital display might be the answer…
Casio G-Lide GLX S5610 2ER Moonphase Watch
Some Casio watches, particularly in the G-Shock range, do display the phases of the Moon. Better yet, these models are often relatively affordable.
Now that you know how your watch's moonphase complication works, ready to learn how to set it?
The moonphase complication differs from other watch complications because it isn't necessarily set the same way. If you regularly read our guides to watch complications, you probably know that most watch functions are adjusted using the crown.
But that isn't always true of a moonphase display… It all depends on the watch!
If you've looked closely at moonphase watches, you may have noticed a small, hidden button on the case. Why hidden? Unlike the pushers that protrude from the side of many watch cases, this one is recessed into the case.
Moonphase setting button on a Schaumburg Watch timepiece
This discreet dedicated button lets you set the watch's moonphase display. It's simple: just press it to turn the disk. But be careful: the button is tiny, and for good reason! Its small size helps prevent accidental presses that could throw off the display without you noticing. Think of it as a safeguard!
To press that tiny button and set your moonphase watch without getting frustrated, use a slender, pointed object. Wooden toothpicks work especially well because their natural material helps prevent scratches.
On some watches, you set the moonphase complication directly with the crown. As a reminder, the “ crown ” is the knob, usually on the right side of the case, that you use to set the time.
Setting the moonphase complication with the crown on a Schaumburg Watch timepiece
To set your watch's moonphase display, pull out the crown and find the position used to adjust that function. Once you've found it, turn the crown clockwise or counterclockwise, depending on the watch.
Knowing how to adjust a moonphase watch is one thing; setting it to the Moon's current phase is even better!
Websites such as Patek Philippe's let you check the Moon's exact phase today or on a date of your choice. Just enter the date into the online calculator to see the corresponding lunar phase.
Moonphase calculator on the Patek Philippe website
Set your moon phase watch accordingly, and you're ready to enjoy this complication every day. Just remember to adjust it every two and a half years to keep it accurate. A reminder on your phone will help you stay on top of it.
From 17th-century clocks to pocket watches and today's wristwatches, the moonphase has always been a complication unlike any other... Its display catches the eye, its reading invites a closer look, and together they leave watch enthusiasts like us dreaming.
Whether it appears in a small window, a large aperture, or on an LCD screen, this complication still gives us plenty to talk about!
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