Every great complication has a first chapter, and for the annual calendar, that chapter was written by Patek Philippe with the reference 5035. Introduced in 1996, it was the manufacture's first annual calendar wristwatch and the first serially produced wristwatch of its kind anywhere in the world. This example, crafted in 18-carat yellow gold with a white dial and applied gold Roman numerals, is a first edition of the complication that went on to become one of the most important in modern watchmaking. It is a piece of horological history that remains as practical and elegant to wear today as it was when it debuted. To understand why the 5035 matters, it helps to understand the problem it solved. A simple calendar watch must be corrected by hand at the end of every month with fewer than 31 days, which means five adjustments each year. A perpetual calendar accounts for every month and every leap year automatically, but it is highly complex and reserved for the very top of a manufacture's catalog. Patek Philippe saw room for something in between, a watch that would distinguish between months of 30 and 31 days on its own and require only a single correction each year, at the end of February. The result was the annual calendar, a complication that combined genuine everyday usefulness with the mechanical ingenuity Patek Philippe is known for. The 5035 made its debut at Baselworld in 1996 and was immediately recognized as a landmark. It was named Watch of the Year shortly after its release, and it established a new category of complication that many other manufactures would later follow. Patek Philippe built an entire family on its foundation, and the annual calendar has remained a pillar of the manufacture's collection ever since. The 5035 was produced until 2005, when it was succeeded by the larger reference 5146, which makes this original reference an increasingly appreciated piece among collectors who value the beginnings of a celebrated complication. The dial is a model of clarity and balance. Its white surface provides a crisp backdrop for applied gold Roman numerals and a railway minute track around the outer edge, while luminous leaf-shaped hands in gold read the hours and minutes. The day of the week appears in a subdial on the left side of the dial and the month in a subdial on the right, each read by a fine central hand that points to the names printed in a circle around it. Below the center, a third subdial displays a 24-hour indication, which helps the wearer tell day from night and set the calendar correctly, and the date is shown through a window at six o'clock. A slender central seconds hand sweeps across the dial, and the Patek Philippe Genève signature sits beneath twelve. The three subdials form a pleasing triangle, giving the dial a sense of symmetry that makes even this much information easy to read at a glance. Inside is the self-winding Calibre 315 S QA, the movement that brought the annual calendar to life. Its name reflects its functions in Patek Philippe's own shorthand, with S for sweep seconds and QA for quantième annuel, the French term for annual calendar. Built on the manufacture's Calibre 315 platform, it uses 35 jewels and is wound by a central rotor in 21-carat gold, with a Gyromax balance regulating its rate. The annual calendar module is designed to recognize which months have 30 days and which have 31, advancing the date, day, and month automatically throughout the year. Only at the end of February, when the month has 28 or 29 days, does the date need a single correction. The movement was finished to the standards of the Geneva Seal, the hallmark of fine Genevan watchmaking at the time, and it can be admired through the sapphire case back. The case is crafted in 18-carat yellow gold and measures 37 mm in diameter, a size that reflects the classic proportions of Patek Philippe's designs from this era. Its two-part construction features a stepped, gently concave bezel and sculpted lugs, along with a sapphire crystal and a transparent screw-down case back. The yellow gold gives the watch a warm, rich glow that pairs beautifully with the white dial and gold numerals, creating a harmonious, timeless look. On the wrist, the 37 mm case sits comfortably and elegantly, suited equally to business and evening wear. This example is fitted to an integrated 18-carat yellow gold bracelet, its polished links echoing the warmth of the case and giving the watch a sense of substance and luxury. The bracelet flows naturally from the case, so the watch feels like a single, unified piece on the wrist. Together, the yellow gold case and bracelet give the 5035 a classic presence that recalls the great gold dress watches of Patek Philippe's past. Collectors value the 5035 not only for its practicality but for its place at the very start of a story. Every annual calendar Patek Philippe has made since, from its successors to the many variations offered today, traces its origins back to this reference. Owning the 5035 means owning the first expression of an idea that changed how the manufacture, and the industry as a whole, approached the calendar watch. What makes the Patek Philippe 5035J so compelling is the way it combines historical significance with everyday usefulness. It is the first edition of Patek Philippe's annual calendar, a Watch of the Year winner, and the beginning of a complication that has become a cornerstone of modern watchmaking. With its white dial, Geneva Seal movement, and warm yellow gold case and bracelet, it offers collectors a genuine piece of horological history that is as rewarding to wear as it is to own.