Since its initial debut in fall 2020, Oris’ in-house Calibre 400 automatic movement has been gradually working its way through the brand’s lineup as its new de facto flagship three-hand powerplant. As one of the cornerstones of Oris’ lineup the Aquis diver was a natural choice to debut the new movement in late October 2020, but at that time the Calibre 400 was restricted only to full size 43.5mm models. As summer 2021 ramps up and enthusiasts search for a new vacation-ready sports watch, Oris takes the next logical step and brings the Calibre 400 to the smaller 41.5mm Aquis line. Rather than reinventing the wheel, the new Oris Aquis Date Calibre 400 41.5mm series lets the performance of its new movement speak for itself while maintaining the classic Aquis look.
As the name suggests, the stainless steel case of the Oris Aquis Date Calibre 400 41.5mm line measures in at 41.5mm. The modern and slightly unorthodox Aquis shape with its slab case sides, heavy wide crown guards, and short angular semi-integrated lugs is shared with previous 41.5mm Aquis models, and like those iterations, the unique proportions of the Aquis may make the case measurements somewhat misleading. In practice, the shrink-wrapped profile of the mid-case without any outward flaring coupled with the abrupt downward slant and short reach of the lugs tend to make the Aquis series feel substantially more compact on the wrist than more traditional diver styles. As with previous versions, the heavily toothed unidirectional dive bezel is noticeably wider than the case beneath it, leading to a slight overhang which should aid grip. The ceramic bezel insert features a bright, legible white diving scale on a base of black, navy blue, or deep forest green. Around back, Oris includes a sapphire display window to showcase the new in-house movement, but despite this more vulnerable element the case is rated at a hefty 300 meters of water resistance.
Like the cases, the dials of the new Oris Aquis Date Calibre 400 41.5mm series keep the overall look familiar while subtly hinting at the new movement within. The most notable difference between these dials and the dials of previous Sellita-powered 41.5mm variants is the 6 o’clock date window. Where the smaller diameter of the Sellita movement forced the date display of those models inboard slightly, leading to both a date window and a shortened index at 6 o’clock, the larger date wheel of the Calibre 400 pushes the 6 o’clock window directly in line with the rest of the faceted applied hour indices, eliminating the 6 o’clock index entirely for a cleaner and simpler look. Outside of this small change and a “5 Days” line of text at 6 o’clock, the dial layout is unchanged, with the familiar rounded sporty alpha handset and indices making a return. Also like many previous Aquis models, all three versions of the new Aquis Date Calibre 400 41.5m series use a sunburst dial finish. Buyers can choose between a dark anthracite gray tone, an oceanic sunburst blue, or an emerald green, which feels deep and intense in initial images.
The in-house Calibre 400 automatic movement inside the Oris Aquis Date Calibre 400 41.5mm series is a major step forward for the brand’s movement-making capabilities, especially for its core offerings. Although accurate within COSC chronometer standards at -3/+5 seconds per day, Oris interestingly does not submit these movements for certification. Beyond the excellent accuracy, the Calibre 400 offers magnetic resistance of up to 2,250 gauss, more than 11 times the current ISO standard for anti-magnetism. This durability is continued through the automatic rotor, which replaces the complex and often delicate ball bearing system with a mechanically simpler and more robust tongue-and-groove metal slide bearing system which Oris claims produces far less wear. Power reserve performance is robust as well, with twin mainspring barrels producing a hefty 120 hours of power reserve at a 28,800 bph beat rate. Oris also touts the longevity of the Calibre 400 platform, recommending a service interval of 10 years rather than the more standard five recommended years between services. While the Calibre 400’s performance is undeniably robust, the movement’s finishing is simple, bordering on industrial. A matte-blasted three-quarter bridge covers up most of the real estate beneath the display caseback besides the balance wheel, and the signed skeleton rotor bears a clean brushed finish.
The semi-integrated stainless steel three-link bracelet with dive extension has historically been a hallmark of the Oris Aquis’ design, and the new Aquis Date Calibre 400 41.5mm line continues the trend. With a sharply tapering profile that flows from a narrow clasp directly into the case and bright polishing on the outer links to visually match the lugs, this bracelet offers a unique and eye-catching look. Oris keeps the bracelet from appearing too monotone or flashy thanks to vertically brushed center links. For those that prefer straps, all three models in the new line can also be optioned with the brand’s signed textured black rubber strap, which also includes a folding clasp and dive extension for a modern and functional sporting look.
Funny, when I unboxed this new Oris Aquis Calibre 400 for this review, I couldn’t stop looking at the dial. I know it should be all about the in-house caliber 400, but I’ll tell you that it took a few minutes before taking the watch off again to have a glance at the new Oris movement.

The dial (and watch) look quite similar to their Aquis Ocean Cleanup limited edition. That watch was a bit smaller, and there are some aesthetic differences, but it just reminded me of that one. If you’re a watch fanatic, you haven’t missed the introduction of the new Oris movement: Calibre 400. It is interesting that Oris decided to introduce the movement first, and a few weeks later introduce the first watch to be powered by it. And here it is, the Oris Aquis Calibre 400. With a beautiful gradient blue dial.
I am not a diver, but I do have and have had my share of divers watches. From all sorts of brands and in all sorts of price ranges. What they all have in common are the typical features for diving purposes. A uni-directional bezel, 300 meters of water resistance, screw-down crown, screw case back, and a very legible dial. This watch is no different when it comes to those features. The Oris Aquis has a case shape that is rather unique, of course. And a proper stainless steel bracelet, with the opportunity to swap it for a rubber strap. But the new in-house movement is what makes this watch stand out. The recently introduced Oris calibre 400 has been discussed in this article, but let me summarize.
On 15th October this year, Swiss watch maker Oris unveiled Calibre 400, the brand’s new generation mechanical self-winding movement featuring enhanced anti-magnetic features and an incredible power reserve of five days.

The much-awaited Oris in-house Calibre 400 set a new standard for automatic mechanical movements. This modern mechanical movement was developed entirely in-house by Oris watchmakers and Engineers. It comes with 10-year recommended service intervals and a 10-year warranty.

On 29th October, the brand announced its new diving watch model Aquis Date Calibre 400, the first Oris timepiece to be equipped with the newly released movement.
Oris’s engineers identified that one of the most frequent issues with automatic mechanical movements concerns the ball-bearing system that allows the free-spinning oscillating weight (or rotor) to rotate. This is a critical element of an automatic watch – as the rotor spins, it generates power that’s stored in the mainspring, which is housed in the barrel.

Oris removed the ball bearing altogether and replaced it with a low-friction slide bearing system, in which a metal stud runs through a lubricated sleeve. This is much less complex, highly efficient, and involves far less wear and tear, making it less prone to breakdowns.
The movement provides an impressive 120 hours (5 days) power-reserve via twin barrels, both of which house an extended mainspring, each long enough to store two-and-a-half days of power.

Most mechanical watch movements will be magnetised if exposed to the strong magnetic forces we encounter in daily life. When this happens, they become less accurate, and can stop altogether. To make it highly antimagnetic, Oris engineered Calibre 400 using more than 30 non-ferrous and anti-magnetic components, including a silicon escape wheel and a silicon anchor. In testing by the renowned Laboratoire Dubois, Calibre 400 deviated by less than 10 seconds a day after exposure to 2,250 gauss.

For context, the latest version of the ISO 764 standard for anti-magnetic watches requires that to qualify as anti-magnetic, a watch must be accurate to within 30 seconds a day after exposure to 200 gauss. Calibre 400 recorded one third of the deviation allowed after exposure to more than 11 times the force permitted, making it a highly anti-magnetic movement.

The movement features 21 jewels and beats at 28’800 vph (4Hz). It follows the three-hands and date lay-out featuring centre hands for hours, minutes and seconds functions and a date window at 6’ o clock.

The Oris 400 movement measures 30.00 mm (13 1/4’’’) diameter. It is larger than Cal. 733 (Base Sellita SW 200-1 movement, 25.60 mm or 11½’’’), which has been used for the Aquis Date models since long time.

The Calibre 400 features the same dial lay-out as the SW 200-1 movement: Three hands and date. The new automatic calibre also incorporates instantaneous date mechanism, date corrector, fine timing device and stop-second. In terms of autonomy, the Calibre 400, which is a twin-barrel movement, provides 120 hours of power reserve where as SW 200-1 offers a power reserve of 38 hours.

Naturally, the first watch to house Oris’s innovative automatic movement is the Aquis Date, a popular model from the brand’s contemporary diver’s watch collection.