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The History of the Moonphase Complication in Horology

Christopher Ward C1 Moonphase

Our daily lives are pretty tuned to the sun. Day and night define our circadian rhythm, our working hours, the frustration behind daylight savings, pretty much our entire concept of daily life. It’s even used as a yardstick for the time of year, with painfully short days in winter, longer in summer. And yet it’s the moon, the sun’s weird, celestial little cousin, that makes its way onto watches. A fact that’s worth investigating, so let’s delve into the history of the moonphase complication and its importance to horology.

The moon has been used as a calendar marker for as long as 35,000 years. No, that comma’s not in the wrong place, we’re talking THIRTY-FIVE millennia here. Referenced in cave paintings, it’s something that every culture on the Earth has used in one way or another – and there are good reasons why.

NASA Moonphases

Image credit: NASA

Unlike the sun, which shifts ever so slightly day after day, the moon changes much more dramatically. There’s a visible difference from one night to the next as it moves through its monthly cycle, making it much clearer and easier to use as a timekeeper. In horological parlance we’d say it’s beating at a much higher frequency than the sun. These clear changes are the reason for the Chinese lunar calendar among many, many others.

Then there’s its real-world effect. Tidal shifts have been historically vital to anyone making a living in coastal waters which, given trade, fishing and countless other uses, is a lot of people. Therefore, understanding the moon and the way its various phases affect the tides, is a practical necessity. Sure, our understanding of why and how the moon does what it does have come a long way – especially since landing on the thing – but it’s always been one of the most important aspects of human culture. These days though, unless you’re a fisherman, it’s also one of the most pointless complications to put on a watch.

St. Marks Clocktower Torre dell'orologio

St Mark’s (Torre dell’Orologio) astronomical clocktower in Venice

Now I’m not saying that’s necessarily a bad thing. Since quartz in the 1970s and mobile phones more recently, the wristwatch has been an obsolete timekeeper, and we still love them. That’s without getting into the ornamentation of metiers d’art; a realistic engraving of Cambodian ruins doesn’t guarantee a COSC certification.

And yet these days it’s one of the most common complications to see among a certain breed of watchmaker, specifically when talking about dress watches, and we’ll get onto that. But before Patek Philippe put the first moon phase into a wristwatch (because of course it was Patek Philippe), the complication already had a rich mechanical history.

Antikythera mechanism

A recreation of the Antikythera mechanism found 2,000 years ago, the world’s first computer used to predict astronomical events.

One of the earliest known, solid examples of a mechanical moon phase is the Antikythera mechanism, most recently famous as the latest Indiana Jones McGuffin. While it’s not some cartographic time machine, it is a piece of pure innovation we’ve discussed before – we interviewed Ludwig Oeschlinn, the creator of the Ulysse Nardin Freak and the man that figured out what the twisted, salvaged mechanism was. It’s a mechanical calendar and indicates among other things the irregular movement of the moon around the Earth.

It only took a couple of millennia for Europeans to catch up with the idea and in the renaissance era astronomical clocks were often found on churches and city landmarks. These clocks were a historical quirk for one fact: they represented the sun and the moon moving around the Earth. They nailed the moon part of the equation, but were discovered to be a little iffy when we started taking a closer look at the solar system.

Patek Philippe First Perpetual Calendar 1898

The first moonphase wristwatch introduced by Patek Philippe in 1925

Moon phases re-appeared in what would become their final form in Germany in the 1700s. It became a template to use the semi-circular space above otherwise rectangular dials to show one half of a disc with two moons on it. This meant that the indicator would move from new moon to full moon and back again, before re-setting as the disc revolved. It was inspired, genuinely useful (at the time) and perhaps most importantly, was absolutely beautiful.

Over the next centuries clockmakers would try and outdo each other to create more ornate moon phases. They were often the highlight of the dial, with happy moons, dour moons, silver, gold, or painted moons, over-the-top or retrained moons of all shapes, sizes and backdrops. Some would bring in other astronomical complications, but the moon phase itself soon became one of the most popular additions to fine clocks.

Patek Philippe Calibre 97975 First Moonphase 1925

Patek Philippe calibre 97975

That kind of embellishment however is slightly at odds with how wristwatches evolved, that’s to say the trenches of WWI. Watches as we understand them now – not tiny, jewellery pieces a la Breguet – were utilitarian and rugged. That’s in large part why it took until 1925 for Patek Philippe to introduce it into their collection in the calibre 97975. That might sound familiar as we touched on it in the last issue, as it’s the movement inside the first perpetual calendar wristwatch, and is in large part the reason for why the two complications are linked in many collectors minds.

Perhaps the bigger impact came from the Rolex 8171 from 1949. Another calendar watch, the 8171 placed the moon phase by itself at six o’clock, making it the focal point of the dial. Since then, rare is the moon phase that mixes up the formula. Even the way it works has rarely been altered since.

Rolex 8171 1950

Rolex 8171 (circa 1950)

Despite its lofty themes, the moon phase is actually one of the easiest complications to implement, provided your movement already has a date. All you need to do is link the moon wheel to the date, which will rotate it a little once each day. Because it takes a whole month to do one revolution, it’s not a ticking you’ll notice. It’s an elegant solution and one that is accurate enough. This is the kind of moon phase that 99 percent of watches will use. But it’s not the only one.

Recently, Christopher Ward brought out what they call a moon phase in perpetual motion in the aptly named C1 Moon Phase. They achieve this by linking the moon phase separately to the date with a module, so that it’s constantly, slowly moving. It also separates date and moon phase which you need for a truly accurate take on the complication.

Hermes Arceau L’Heure De La Lune Blue Pearl

Hermes Arceau L’Heure De La Lune Blue Pearl

There are also versions that use awesome display methods like the Hermes Arceau l’Heure de la Lune, which goes completely off the deep end and moves the ‘dials’ across the moon indicators, rather than the other way around. It’s one of my favourite versions out there. Or there’s the Ochs & Jnr Selene Nebra Moonphase, which actually pays tribute to that early Greek astronomical clock – fitting as it’s designed by none other than Oeschlinn.

Ochs Und Junior Selene Nebra Moonphase

Ochs Und Junior Selene Nebra Moonphase designed by Ludwig Oeschlinn

However, if there’s one watchmaker working today recognised as the master of the moon phase, it’s Andreas Strehler. I don’t mean colloquially; his Sauterelle à Lune Perpétuelle holds the Guinness World Record for most accurate moon phase. In numbers, this is because it will be out by a day every 2.045 million years (although since the world record was awarded in 2014, the industry has continued to improve accuracy – check out the IWC Eternal Calendar). It would take longer than the entire history of moon phase watches – of humans using the moon as a calendar at all – before it needs adjusting.

Andreas Strehler Sauterelle à Heure Mondiale

Andreas Strehler Sauterelle à Heure Mondiale

How? An incredibly complicated set of calculations and patented fine machining that’s hard for seasoned watchmakers to wrap their heads around, let alone a humble (ish) horological writer. Why? Because even though moon phases aren’t strictly useful, they tie into multiple facets of why we love watches. They’re beautiful, inspirational, gloriously unnecessary; they tap into a millennia-old fascination with the night sky and the passage of time both. They’re one of the oldest complications in watchmaking and, whether it’s a simple addition to the date wheel or a mind-blowing tour de force of mathematical obsession, they’re here to stay for many more millennia to come.

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About the author

Sam Kessler

Legend has it that Sam’s first word was ‘escapement’ and, while he might have started that legend himself, he’s been in the watch world long enough that it makes little difference. As the editor of Oracle Time, he’s our leading man for all things horological – even if he does love yellow dials to a worrying degree. Owns a Pogue; doesn’t own an Oyster Perpetual. Yet.