Among its many notable 2021 debuts, Patek Philippe earlier this month unveiled two particularly interesting calendar watches. Each introduces a new approach to full-spectrum timekeeping, and, notably, neither debut is cased in gold.
One, the much-discussed in-line Perpetual Calendar (Ref. 5236P-001), is a new perpetual calendar that shows the day, date, and month in a single panoramic aperture at the top of the dial –the first such display in a Patek Philippe wristwatch.
The second calendar model, the Ref. 4947/1A-001 Annual Calendar, places an annual calendar in a steel case and on a steel bracelet. Recall that Patek Philippe pioneered the annual calendar for the wrist in 1996, and this new model is the brand’s first annual-calendar-only watch not cased in a precious metal.
The Perpetual Calendar
Patek Philippe has previously created in-line calendar displays, but strictly for pocket watches. Interestingly, these were made first for the American market. One example from 1972 (No. P- 1450) features a calendar format in the American style (“à l’américaine”), showing month, date, and then day.
Taking a cue from this historic model and a few others, Patek Philippe several years ago challenged itself to devise such a display in miniature for a wristwatch.
Patek Philippe’s watchmakers decided to design a system with two date disks – one for the tens and one for the units. This meant that the entire calendar display would require four disks, one for the day, two for the date, and one for the month, and all needed to be embedded in the same plane.
Stay thin
To accomplish this, and to maintain a thin caliber, Patek Philippe’s watchmakers built the new movement based on the caliber found in the Ref. 5235 Annual Calendar Regulator from 2011. The caliber in the Ref. 5235 features an off-center micro-rotor, which opens up space for the additional 118 components required to construct the in-line display.
Patek Philippe then had to re-engineer the caliber to more efficiently drive the extra energy required by a perpetual calendar. The firm’s watchmakers increased the torque of the spring barrel 20 percent and boosted the winding power by utilizing a platinum rotor rather than the more typical gold rotor.
And finally, Patek Philippe improved the caliber’s overall rate stability by increasing the frequency from 3.2 to 4 Hz (28,800 semi-oscillations per hour).
The resulting new automatic, ultra-thin caliber 31-260 PS QL boasts a recessed mini-rotor and a customized module for which Patek Philippe has filed three patents. In addition to powering the date display, the movement also powers two round displays that show the leap-year cycle as well as the day/night indications. A further window displays the moon phases.
Patek Philippe is launching the Perpetual Calendar Ref. 5236P-001 in a hand-polished 41.3mm x 11.07mm platinum case. Its handsome blue dial offers nicely gradated black at the edges. It arrives on a matching navy blue alligator leather strap secured with a fold-over clasp. Price: $130,108.
Annual Calendar
The new Patek Philippe Ref. 4947/1A-001 Annual Calendar finds the manufacturer re-designing the ultra-practical complication to fit within a steel Calatrava case for the first time. Equally interesting, the Calatrava is attached to an all-new steel bracelet.
You might recall that Patek Philippe invented the wrist-borne Annual Calendar in 1996, effectively creating an entirely new calendar watch category for itself (and many other high-end watchmakers.)
Requiring only one manual correction per year (at the end of February), the annual calendar brings with it a convenient, and moderately priced, calendar function to those who would like the all-encompassing coverage of a perpetual calendar, but balk at the high cost of nearly all examples of the mechanical complication.
Until this new model, Patek Philippe has offered its annual calendar in various ladies’ and men’s models, all in either gold or platinum cases.
The new 38mm steel-cased Patek Philippe Ref. 4947/1A-001 Annual Calendar offers a polished steel bezel that matches the new, totally integrated steel bracelet. Patek Philippe has created a luxurious five-row bracelet made of fully polished links and a fold-over clasp.
The blue dial on the new watch is patterned with vertical and horizontal satin finishes that appear textured, as on a matte linen fabric. This assures that the dial contrasts nicely with polish of the case and bracelet, creating a surprisingly contemporary overall appearance. 
The watch’s calendar displays are easy to read: Two subsidiary dials between 9 and 10 o’clock indicate the day and, between 2 and 3 o’clock, the month; the date appears in an aperture at 6 o’clock just below a moon-phase display rounds out the calendar functions.
From the back, the wearer can enjoy a clear view of the beautifully finished automatic Patek Philippe caliber 324 S QA LU movement. The watch is nicely sized at 38mm and not too fussy, particularly given its array of calendar functions. It also holds a unique position within the Patek Philippe lineup, especially with its steel case and bracelet. If you’ve been waiting for a steel-cased Patek that is not a Nautilus and not a chronograph, this might be your new watch. 
Price: $47,904
Specifications: Patek Philippe Perpetual Calendar (Ref. 5236P-001)
Movement: Self-winding mechanical Caliber 31‑260 PS QL. In-line perpetual calendar. Day, date, month, leap year and day/night indication in apertures. Small seconds.
Dial: Blue, black-gradient, vertical satin finish, gold applied hour markers.
Case: 41.3 by 11.07 platinum. Interchangeable solid and sapphire crystal case backs. Water-resistant to 30 meters.
Bracelet: Alligator leather with square scales, hand-stitched, shiny navy blue. Fold-over clasp.
Price: $130,108.
Specifications: Patek Philippe Annual Calendar (Ref. 4947/1A-001)
Movement: Self-winding mechanical movement. Caliber 324 S QA LU. Annual Calendar. Day and month by hands. Date in an aperture Moon phases. Sweep seconds.
Dial: Blue, vertical and horizontal satin-finish (“shantung” finish), gold applied numerals.
Case: 38mm by 11mm steel, sapphire crystal case back, water-resistant to 30 meters.
Bracelet: Steel. Fold-over clasp.
Price: $47,904
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