July 23, 2021

Patek Philippe: Ref. 5236P-001 In-line Perpetual Calendar

Patek Philippe presents a new perpetual calendar that displays the day, the date, and the month on a single line in an elongated aperture beneath 12 o’clock. To combine this unique feature with crisp legibility and high reliability, the designers developed a new self-winding movement for which three patent applications have been filed

Patek Philippe Ref. 5236P-001 In-line Perpetual Calendar

As classic grand complications par excellence, perpetual calendars have always been prominently featured in Patek Philippe’s collections. In 1925, the Genevan manufacture presented the first wristwatch with this highly elaborate complication (movement No 97’975)

Patek Philippe perpetual calendars offer a wide range of design elements with analog or aperture displays and dial configurations. Models with the famous self-winding ultra-thin caliber 240 Q movement, such as the Ref. 5327, can be recognized by their day, date, and month displays in three separate subsidiary dials. The self-winding caliber 324 S Q, which among others powers the Ref. 5320, exhibits another traditional face among the manufacture’s perpetual calendars. It features 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 also ticks in the Ref. 5160 and features an added complication: the date display with a retrograde hand that sweeps an arc from 8 to 4 o’clock. It is complemented with four aperture displays for the day of the week at 9 o’clock, the month at 3 o’clock, the leap year cycle at 12 o’clock, and the moon phases at 6 o’clock. 


With the launch of the Ref. 5236P-001, Patek Philippe gives the perpetual calendar a new face.

Patek Philippe Ref. 5236P-001 In-line Perpetual Calendar

For the new Ref. 5236P-001, this watch presents an innovative indication of the day, date, and month in an elongated aperture at 12 o’clock. A panoramic aperture of this kind is not totally unprecedented in the manufacture’s collections.

Patek Philippe Ref. 5236P-001 In-line Perpetual Calendar

In the course of time, the manufacture had already crafted pocket watches with an in-line calendar display for the American market. Customers in the new world were enthusiastic about complicated watches that were easy to operate and showed the indications of the perpetual calendar at a glance. One example of such timepieces is on display at the Patek Philippe Museum: it is a pocket watch from 1972 (No. P- 1450) that features a calendar format “à l’américaine” (month, date, day). 

But never before has the manufacture introduced a wristwatch with a full calendar on a single line as exemplified by the new Ref. 5236P-001

To implement this masterpiece of miniaturization, Patek Philippe had to overcome totally new technical challenges. To assure the largest possible calendar display on a single line with optimized legibility, the developers were asked to design a system with two date disks – one for the tens and one for the units. So the calendar display consists of four disks, one for the day, two for the date, and one for the month – all four perfectly embedded in the same plane

A single date disk with 31 numerals would have been too small and less easily legible. In compliance with the manufacture’s basic principles as set forth in the directives of the Patek Philippe Seal, the new, complex mechanical ensemble had to be implemented with the smallest possible diameter and minimized height without compromising its maximum long-term dependability. For this reason, the project team proceeded on the basis of the caliber 31-260 REG QA that was originally launched in 2011 with the Ref. 5235 Annual Calendar Regulator. Not least because of its eccentric recessed minirotor, this self-winding movement with subsidiary seconds at 6 o’clock is extremely slender.


While retaining the diameter and height of the basic movement, the engineers completely reworked the new caliber 31-260 PS QL (PS for petite seconde and QL for “quantième perpétuel en ligne“) and integrated the manufacture’s latest technical achievements. The movement was “tuned”, so to speak, so it could drive the particularly energy-hungry perpetual calendar mechanism. The torque of the spring barrel was increased by 20% and the winding power boosted with a platinum minirotor. Rate stability was improved by increasing the frequency from 3.2 to 4 Hz (28,800 semi-oscillations per hour) which also simplifies precision adjustments to the rate tolerance specified by the Patek Philippe Seal. 

Patek Philippe Ref. 5236P-001 In-line Perpetual Calendar

Moreover, the caliber 31-260 PS QL is fitted with a reduction wheel that uncouples the automatic winder as soon as the movement is being manually wound. This is a Patek Philippe invention patented in 2019 that reduces wear. The aesthetic appeal of the movement is subtly evolved with two distinctive bridges for the escapement and the fourth wheel. Their configuration affords a better view of the basic movement’s wheel train, overall architecture, and refined finissage as revealed by the sapphire-crystal caseback. This back can be substituted with a solid platinum back that is delivered with the watch


Three patent applications were filed by Patek Philippe for the perpetual calendar mechanism with an in-line display developed for the Ref. 5236P-001. 

Display mechanism (ball-bearing display) – This display system featuring two “double ball bearings with coplanar balls” makes it possible for all the indications of the perpetual calendar to appear on one line in the same plane and without overlapping. 

Shock absorber mechanism and/or anti-double-jump feature for watch movements – This mechanism improves the reliability of the date display as well as the perfect 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. 

Date: Switch from 31 to 01 – This mechanism assures that the unit remains in its position when the switch from the 31st to the 1st of the following month takes place. This is handled by a 31-point star from which two teeth were removed. 


The new Ref. 5236P-001 in platinum are inspired by the Ref. 5235 Annual Calendar Regulator. It features a very sleek case with a diameter of 41.3 mm, a chamfered bezel and a vertical satin finish blue dial

As in most of Patek Philippe’s platinum wristwatches, the case flank features a small diamond at 6 o’clock

The progression of time is tracked with applied hour markers and baton hands in white gold. The technical accent of the railway track minute scale is echoed by the subsidiary seconds scale at 6 o’clock. The day, date, and month displays are clearly and legibly printed in blue on white. A blue alligator strap with a platinum fold-over clasp rounds out  the new Ref. 5236P-001 Perpetual Calendar with perfection. (Price € 115.060)

Patek Philippe Ref. 5236P-001 In-line Perpetual Calendar