An In-Depth Look At The Patek Philippe In-Line Perpetual Calendar, Ref. 5236P

By Nancy Olson

There’s a lot to get excited about when it comes to Patek Philippe’s just-introduced timepieces, but my clear favorite is the In-line Perpetual Calendar, Ref. 5236P-001. Not only is it the latest in the company’s serious history in producing notable calendar watches, it is also the venerable Swiss brand’s first wristwatch displaying the day, date and month in a single line. Three patent applications were filed for the new self-winding movement that drives it, Caliber 31-260 PS QL.

Quick history of Patek Philippe and Calendars

Perpetual calendars have long been a part of Patek Philippe’s oeuvre, dating to 1925 when the manufacture first presented a wristwatch with this grand complication. Various dial configurations followed, with analog or aperture displays. Models fitted with the self-winding ultra-thin caliber 240 Q, for example, are recognized by their day, date and month displays in three subsidiary dials, while watches fitted with the caliber 324 S Q feature a dual aperture for the day and month at 12 o’clock and a subsidiary dial at 6 o’clock for the analog date and the moon-phase display. The caliber  324 S QR  powers the Ref. 5160, features the date display with a retrograde hand and four aperture displays: the day of the week at 9 o’clock, month at 3 o’clock, leap year cycle at 12 o’clock and moon phases at 6 o’clock.

Patek Philippe Ref. 5236P In-Line Perpetual Calendar watch for 2021

In yet another dial design, the new Ref. 5236-P presents the day, date and month in a single line in a panoramic aperture at 12 o’clock. This In-line Perpetual Calendar is inspired by pocket watches created years ago by Patek Philippe specifically for the American market, which included in-line displays in the typical “l’Americaine” format of month, date and day. This style was heretofore considered near impossible to translate to the confines of wristwatch, while still making the calendar display decidedly legible.

The new watch’s platinum case is 41.3mm, with a two-position crown and a sapphire crystal caseback. Three correctors—for the day, date and month—are recessed in the case flank between 9 and 2 o’clock. The moon phase corrector is at 8 o’clock.

Faceted hour markers adorn the satin-finished blue lacquer dial; the central hours and minute hands are in white gold, as is the subsidiary seconds hand. Day/night indication is at 8 o’clock, the leap year cycle is shown at 4 o’clock, and the phases of the moon and subsidiary seconds are at 6 o’clock. And while there’s lots revealed in the limited space of the dial, the overall impact is clean and dignified.

Three patent applications on the Patek Ref. 5236P

The new Caliber 31-260 PS QL required 118 additional parts over and above those normally found in a conventional calendar display, and three patent applications were filed in the process of its development.

The first is for the display system, which features two co-planar double ball bearings, which makes it possible for the indications of the perpetual calendar to appear on one line, in the same plane, and without overlapping. The second patent application is for the shock absorber mechanism and anti-double-jump feature. This improves the reliability of the date display and the synchronization of the two numeral disks by suppressing a second jump of the date in the event of a jolt or when the date is being corrected.

The third patent was filed for the date mechanism to insure a smooth transition when the switch from the 31^st to the 1^stof the following month takes place. A 31-point star from which two teeth were removed was engaged for this purpose. This incredible feat of imagination and engineering is fitted on a hand-stitched blue alligator leather strap and may adorn your wrist for a cool $130,108.