INSTANTANEOUS DATE AND CYCLOPS LENS
The Datejust revolutionized wristwatch date display. Traditionally, the days of the month were marked around the edge of the dial, and a hand pointed to the day’s date. With the Datejust, Rolex introduced a calendar that displayed the date via a disc in a window at 3 o’clock. This would become the watchmaking standard. In 1953, the Cyclops lens was added to the crystal, magnifying the date for easy reading. In 1956, the date change became instantaneous. Rapid, secure setting of the date by turning the winding crown in either direction was introduced in 1977 on models of the Datejust equipped with a medium-sized or large calibre, then from 1983 on those fitted with a small movement.

THE DATEJUST, SUPERLATIVE CHRONOMETER CERTIFIED
Like all Rolex watches, the Datejust is covered by the Superlative Chronometer certification redefined by Rolex in 2015. This exclusive designation testifies that every watch leaving the brand’s workshops has successfully undergone a series of tests conducted by Rolex in its own laboratories and according to its own criteria. These certification tests apply to the fully assembled watch, after casing the movement, guaranteeing superlative performance on the wrist in terms of precision, power reserve, waterproofness and self-winding. The Superlative Chronometer status is symbolized by the green seal that comes with every Rolex watch and is coupled with an international five-year guarantee.

The precision of every movement – officially certified as a chronometer by the Swiss Official Chronometer Testing Institute (COSC) – is tested a second time by Rolex after being cased, to ensure that it meets criteria for precision that are far stricter than those of the official certification. The precision of a Rolex Superlative Chronometer is of the order of −2/+2 seconds per day – the rate deviation tolerated by the brand for a finished watch is significantly smaller than that accepted by COSC for official certification of the movement alone.

The Superlative Chronometer certification testing is carried out after casing using state-of-the-art equipment specially developed by Rolex and according to an exclusive protocol that simulates the conditions in which a watch is actually worn and more closely represents real-life experience. The entirely automated series of tests also checks the waterproofness, the self-winding capacity and the power reserve of 100 per cent of Rolex watches. These tests systematically complement the qualification testing during development and production, in order to ensure the watches’ reliability, robustness, and resistance to strong magnetic fields and to shocks.

THE OYSTER CASE, SYMBOL OF WATERPROOFNESS AND ELEGANCE
The Datejust’s Oyster case, 31, 36 or 41 mm in diameter and guaranteed waterproof to a depth of 100 metres (330 feet), is a paragon of robustness and elegance. The middle case is crafted from a solid block of Oystersteel or from 18 ct yellow, white or Everose gold. The case back, edged with fine fluting, is hermetically screwed down with a special tool that grants only certified Rolex watchmakers access to the movement. The Twinlock winding crown, fitted with a double waterproofness system, screws down securely against the case. The bezel can be smooth, domed, fluted or set with diamonds. The crystal, with a Cyclops lens at 3 o’clock for easy reading of the date, is made of virtually scratchproof sapphire and benefits from an anti-reflective coating. The waterproof Oyster case provides optimal protection for the movement it houses.

CALIBRES 2236 AND 3235
Datejust models are equipped with calibre 2236 (Datejust 31) or calibre 3235 (Datejust 36 and Datejust 41), self-winding mechanical movements entirely developed and manufactured by Rolex. Consummate demonstrations of technology, these movements carry a number of patents. They offer outstanding performance, particularly in terms of precision, power reserve, convenience and reliability.

Calibre 2236 is fitted with the patented Syloxi hairspring in silicon, manufactured by the brand. In addition to resisting strong magnetic fields, this hairspring offers great stability in the face of temperature variations as well as high resistance to shocks. Its geometry, which is also patented, ensures the movement’s regularity in any position. Calibre 2236 includes a paramagnetic nickel-phosphorus escape wheel.

Calibre 3235 incorporates the patented Chronergy escapement, made of nickel-phosphorus, which combines high energy efficiency with great dependability and is also resistant to strong magnetic fields. This movement is fitted with the blue Parachrom hairspring, manufactured by Rolex in a paramagnetic alloy. In addition to resisting strong magnetic fields, this hairspring offers great stability in the face of temperature variations as well as high resistance to shocks. It is equipped with a Rolex overcoil, ensuring the calibre’s regularity in any position.

The oscillator of these two calibres has a balance wheel with variable inertia regulated extremely precisely via gold Microstella nuts. It is held firmly in place by a height-adjustable traversing bridge enabling very stable positioning to increase shock resistance. The oscillator is also mounted on the Rolex-designed, patented high-performance Paraflex shock absorbers, further enhancing the movements’ shock resistance.

Calibre 2236 and calibre 3235 are equipped with a self-winding system via a Perpetual rotor, which ensures continuous winding of the mainspring by harnessing the movements of the wrist to provide constant energy. Calibre 2236 offers a power reserve of approximately 55 hours, while the power reserve of calibre 3235 extends to approximately 70 hours thanks to its barrel architecture and the escapement’s superior efficiency; moreover, since 2023, its oscillating weight has been fitted with an optimized ball bearing.

The Datejust’s movements will be seen only by certified Rolex watchmakers, yet they are beautifully finished and decorated. Since 2023, calibre 3235 has also been marked with the words ‘Chronometer Perpetual’ and ‘Superlative Adjusted’ engraved respectively on the oscillating weight and on the bridges.

OYSTER, JUBILEE AND PRESIDENT BRACELETS
The Datejust 31 is available on a three-piece link Oyster bracelet equipped with a Rolex-designed, patented Oysterclasp, or on a five-piece link Jubilee bracelet – created in 1945 especially for the Datejust – or a three-piece link President bracelet, both of which are fitted with a concealed Crownclasp, developed by the brand and patented. The Datejust 36 and the Datejust 41 are available on a three-piece link Oyster bracelet or a five-piece link Jubilee bracelet with an Oysterclasp.

Bracelets equipped with an Oysterclasp feature the Easylink comfort extension link, developed by Rolex, which allows the wearer to easily increase the bracelet length by approximately 5 mm, for additional comfort in any circumstance.

The President bracelet, fitted on all of the 18 ct gold versions (Datejust 31), includes ceramic inserts – designed by Rolex and patented – inside the links to enhance its flexibility and longevity.