In order to accommodate months with 31, 30 and 28 days, and february 29 in leap years, a movement must have a mechanical “memory” of four years – or 1,461 days. This function requires a highly sophisticated mechanism, based on a complex system of levers and cams pivoting around their axes. This is a domain in which Patek Philippe has repeatedly leveraged its long-standing competence.
Mechanical self-winding movement. Caliber 324 S QR. Perpetual calendar with retrograde date hand. Moon phases. Day, month, leap year in apertures. Sweep seconds hand. Opaline-white dial, hand-guilloched center. Fold-over clasp. Case: yellow gold. Sapphire-crystal case back protected by a hinged dust cover. Water resistant to 30 m. Case diameter: 38 mm. Height: 11.8 mm.