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Review: Ochs Und Junior Annual Calendar

You might remember we recently reviewed watchmaking mastermind Ludwig Oechslin’s MIH watch, an annual calendar that took a basic movement and added just nine parts to give it full annual calendar capability. Well apparently that wasn’t an achievement enough, because he’s done it again—this time the part count has been reduced to just three.

A big thanks to the owner of this watch who very kindly loaned it to us for review. If you have a collection of interesting and unusual watches that really stand out, please get in touch at


If you recall, Oechslin is a man who became a theoretical physicist so he could master the mathematical understanding of a mechanical watch in the purest and most elegant way. And it doesn’t get much more elegant than just three extra parts. The movement started life as an ETA 2824-2, a time and date calibre with 38 hours of power reserve and self-winding rotor. We’ll get on to the wizardry of the annual calendar in a minute, because when it comes to Oechslin’s pursuit for simplicity, even the time doesn’t get away with being left untouched.

The hour and minute hands are as you’d expect. They operate as you’d expect. But the dial, peppered with more holes than the Red Baron’s plane, makes reading them a challenge you might not have expected. Here’s the thinking: on a normal watch, there’s a marker for each hour and a marker for each minute, which do double duty with seconds. Oechslin thought, however, why have a marker for each hour and each minute? If you have one for every other, you read the gap between as the missing marker. So, hours 12, 2, 4, 6, 8, and 10 are visible. When the hour hand points in between, it’s, well, in between.

What about the minutes? Same idea. See those holes around the dial just inside the hour markers? I’ll tell you what those are for in a moment, but for now they’re your minute markers, and so are the gaps in between. However many holes the minute hand has passed, double it and that’s your minute reading. And seconds? There’s a running indicator in the middle, capping the hand stack.


If you’re still figuring out exactly how the time’s read, then hang on to your hats because that was just the warm-up. Those of you who are the brains of the bunch will have noticed that the markers we used for the minutes actually number, thanks to a single marker overlap, thirty-one. There are of course thirty-one days in the longest month, ergo this is also the date display.

Oechslin didn’t have to do a whole lot here since the date already exists as a feature in the ETA 2824. The mechanism is near-as-you-like the same, but the way you read it is not. It’s quite simple: starting at the first marker on the inside of the eccentric spiral, each hole represents a day. The one that’s filled in with colour is the one you read.

You don’t have to count them all though. You can read the minutes and divide by two as a quick shortcut. Say the hole next to the forty-minute marker is the one indicating the date; divide in two and you’ve got the twentieth. For dates either side of divisible markers, you can find a nearby reference and count up or down. Simple!


If you’re still with us, then hang on because things are about to take a turn for the crazy. As this is a calendar watch, we don’t just get the date but we get the day as well. Sitting at the lower half of the austere dial is a smaller set of bullet holes that number seven in total. Yep, this is the day indicator.

To add the day indicator to the basic movement, Oechslin needed just one extra part. By modifying the hour rod collar to add a finger, the watch can rotate the weekday wheel once every twelve hours to display the day. There’s a lot to unpack here: one, how is the mechanism and the display all one part? Two, how does the day display work if it’s rotated every twelve hours and not twenty-four? Three, why does my brain feel like a puddle in the back of my skull?

All good questions, and the answers are surprisingly simple. Normally an extra display would require at least three different parts: the display itself, the wheel to drive the display and something to hold it in place. Well, here the wheel is the display, the print applied straight to it, and it’s held in place by the dial itself, which has been modified to house it.

The second question is not only simply answered, but what at first seems like a flaw has actually been turned into a feature. The hour mechanism with the modified collar drives the weekday wheel forward once a rotation—every twelve hours—and so with some clever placement of print, the day display is also a day/night display. In the morning, only the present day is shown; in the afternoon, when the wheel is advanced forwards after midday, the present and next day are both shown.

So which day is which? Whichever you like! Monday your least favourite day? Put it at the bottom. Think of Wednesday as hump day? Stick it at the top. You can make it whatever you like.


The real party trick of this watch, however, is that it only needs the date changing once per year on the first of March. An annual calendar like this, therefore, needs to differentiate between months of thirty and thirty-one days, and to do that usually requires some forty-odd parts. For Oechslin, on top of the day display, he added just two.

By now you’ll have probably guessed that the last remaining display at the top, the one with twelve holes, is the month. January is top and on the left, going around anti-clockwise. These ones are specific—you can’t pick what you like as you can the day. Like the day, the display is printed straight to the wheel and held in place by the dial.

The two parts that make the month display work feed from the date mechanism. There’s a smaller gear, a star shape with five teeth, which meshes between the date and the second of the two additional parts, the month wheel. The month wheel has twenty-four teeth, five of them—unequally distant—a little longer. It’s this wheel that represents the genius of Oechslin in a single piece.

Every month, the date advances the month wheel two teeth via the star-shaped piece, making twelve advancements total. That’s all fine for months with thirty-one days—but what about the months of just thirty? That’s where those longer teeth come into play. Remember that modified hour rod collar with the extra finger? That interacts with the longer teeth on the month wheel to give it an extra push just on those shorter months, nudging the date indication so it skips the 31st and goes straight to the 1st.

There’s no springs, no levers, no complexity—just those two extra parts. Oechslin chose the approach to keep the watch serviceable and make it more robust where levers and springs can be fragile and difficult to service. The added side effect of that is the entire watch can be set with just the two positions of the crown.

The Ochs Und Junior Annual Calendar is as absolute marvel of creative thinking. The reduced complexity means reduced cost, too, around $8,000 where other annual calendars would cost many times that. And, as if to emphasise the focus on simplicity and engineering, the case itself—available in titanium or silver, in 42, 39 or 36mm—has a completely bare-bones finish that still bears the hallmarks of the machine that made it. There’s 100m of water-resistance thrown in too for good measure to remind you that this high complication is made for wearing every day. If I had one, I know I would.