Tested by Rolex with newly-developed methodology and high-technology, along with official COSC certification, the new Day-Date redefines the status of Superlative chronometer, with criteria for chronometric performance twice as exacting as those for an officially certified chronometer. The newly introduced perpetual self-winding 3255 caliber with 14 patents, entirely developed and manufactured by Rolex, also sets new standards for resistance to shock and magnetism, power reserve, reliability and ease of use. It features innovations such as the new and more efficient Chronergy escapement, the more resilient blue Parachrom spring in the oscillator, as well as the new-generation Perpetual rotor for more rapid winding. The 40mm 18K yellow gold Oyster case with fluted bezel features scratch-resistant sapphire and Cyclops lens over the date window. With a screw-down case back and Twinlock double waterproofness system for the screw-down crown, it is water resistant to 100m. The watch is worn on the wrist with an 18K yellow gold President bracelet with semi-circular three-piece links and a concealed deployment Crownclasp. The beautiful champagne dial features centre hands for hours, minutes and seconds, as well as instantaneous day and date in apertures.