The Audemars Piguet Royal Oak Perpetual Calendar is a Royal Oak with a perpetual calendar complication: a mechanism that tracks the day, date and month and accounts for the different month lengths and leap years without manual correction in normal use. Both generations use a 41 mm case; across them the watch comes in steel, titanium, gold and ceramic. This guide explains how the calendar works, how the movement generations differ, which metals exist and what to check before buying. Bizak & Co. is a sourcing desk: we find a specific watch on request, we do not hold these in stock, and nothing here is a listing.
Last reviewed on October 28, 2026 by Filip Biczak. Details are drawn from Audemars Piguet's own pages where possible, and anything we could not confirm there is flagged as such. Sources: Audemars Piguet, new perpetual calendar and Audemars Piguet, Royal Oak Perpetual Calendar.
What is the AP Royal Oak Perpetual Calendar?
It is the Royal Oak case and integrated bracelet design fitted with a self-winding perpetual calendar movement. Unlike a simple date watch, a perpetual calendar mechanically knows which months are short and which years are leap years, so it keeps showing the right date through those changes. Audemars Piguet describes the perpetual calendar as a complication that has shaped the brand since its beginnings. The Royal Oak version pairs it with the octagonal bezel and Grande Tapisserie dial pattern that the collection is known for. For the wider family, see our Audemars Piguet Royal Oak guide.
How does the perpetual calendar display work?
The dial reads the day, date and month on separate indicators, plus a leap-year indicator, and the movement advances them together. On the current generation, Audemars Piguet places the day at 9 o'clock, the date at 12 o'clock, and the month and leap-year indicator at 3 o'clock, with the week shown on the inner bezel. On the earlier 26574 generation, Audemars Piguet lists an astronomical moon phase at 6 o'clock. Dial designs differ between versions, so confirm the exact layout, moon phase included, on the reference you are considering. Correction is done through the crown on the newest movement, which Audemars Piguet calls an all-in-one crown.
What is the difference between caliber 5134 and caliber 7138?
Caliber 5134 powered the 41 mm reference 26574 from 2015, and caliber 7138 arrived in 2025 on the 26674 generation. Audemars Piguet says the 5134 adapted its perpetual calendar movement to a larger case while keeping a thickness of 4.3 mm, and it calls the John Mayer limited edition the last one equipped with it. The 7138 is a new in-house movement about 4.1 mm thick, with all calendar functions on one layer and corrections made through the crown. Reported case dimensions are about 41 mm across and 9.5 mm thick for both generations, which is why the two look so similar on the wrist.
| Generation | Reference family | Caliber | Case diameter | Movement thickness | Notable point |
|---|---|---|---|---|---|
| Earlier 41 mm | 26574 | 5134, self-winding | 41 mm | 4.3 mm | Introduced the 41 mm perpetual calendar in 2015 |
| Current 41 mm | 26674 | 7138, self-winding | 41 mm | 4.1 mm | All-in-one crown for corrections; launched in 2025 |
What case sizes and metals does it come in?
The standard case is 41 mm, offered in stainless steel, titanium, gold and ceramic. Examples we can point to include steel and titanium versions (the 26574 family included a titanium 26574TI), pink gold (26574OR) and white gold (26574BC) on the earlier generation, and steel, sand gold and blue ceramic (26674CD) on the current one. Metal choice affects weight, finish and how easily the market absorbs a watch, so decide on it early.
| Reference | Case material | Generation |
|---|---|---|
| 26574ST | Stainless steel | Caliber 5134 |
| 26574TI | Titanium | Caliber 5134 |
| 26574OR | Pink gold | Caliber 5134 |
| 26574BC | White gold | Caliber 5134 |
| 26674ST | Stainless steel | Caliber 7138 |
| 26674CD | Ceramic | Caliber 7138 |
What should you check when sourcing one?
Confirm the exact reference, the generation, and the paperwork before anything else. Because the two generations look alike, the reference on the case back and papers is the only reliable way to tell a 5134 watch from a 7138 watch. Ask for the full set, the service history, and any limited-edition numbering, and check that the calendar advances correctly through the month end. Our authenticity page sets out what we verify. You can browse the Audemars Piguet Royal Oak Perpetual Calendar models we can source, the broader Audemars Piguet Royal Oak collection or the full Audemars Piguet range.
Quick answers
What is an AP perpetual calendar?
It is a watch whose mechanism tracks day, date, month and leap years on its own. In normal use it needs no manual correction at month ends, and the Royal Oak version offers it in the brand's signature case.
How big is the Royal Oak Perpetual Calendar?
The current references are 41 mm in diameter, and the earlier 26574 is also 41 mm. Reported thickness is about 9.5 mm, but confirm it on the specific reference.
Which movement is in the Royal Oak Perpetual Calendar?
Caliber 5134 in the 26574 generation and caliber 7138 in the 26674 generation. Both are self-winding in-house movements from Audemars Piguet.
Does Bizak & Co. hold these watches in stock?
No. We source on request, confirm the exact unit and terms with you, and only then proceed.
Related reading: Audemars Piguet Royal Oak guide and Royal Oak Tourbillon guide.
Get your Audemars Piguet sourced
Tell us the model, size, dial and bracelet preference, whether you want new or pre-owned, and your budget and timing, through our sourcing enquiry form. We confirm the specific watch, photographs and final price before you commit, so you can decide against a real target. A $200 deposit, credited to the price, starts the search.
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