Audemars Piguet perpetual calendars explained: references and service

An Audemars Piguet perpetual calendar is a mechanical watch that shows the day, date, month and moon phase and adjusts for the different lengths of months and for leap years without manual correction, and the Royal Oak Perpetual Calendar is the reference most buyers mean. The current core model is the 41 mm Royal Oak Perpetual Calendar 26574, offered in steel, rose gold and other materials, with a ceramic variant in the 26579CE. This guide explains how the perpetual calendar works, which references matter, what service involves, how the Audemars Piguet compares with the Patek Philippe Nautilus perpetual calendar, dated catalogue prices in 2026 and what to check before buying. Bizak & Co. sources these watches to order; the Royal Oak collection lists the configurations we can seek.

Last reviewed on September 29, 2026 by Filip Biczak. Prices are dated observations, not quotes.

How does an Audemars Piguet perpetual calendar work?

A simple calendar watch knows that months have 31 days, so it needs a manual correction at the end of each 30-day month and again in February. A perpetual calendar carries a small mechanical program, in effect a cam that completes one turn every four years, which tells the date mechanism how long the current month is. The watch therefore switches from the 30th to the 1st in April, June, September and November, jumps from the 28th to the 1st in a common February, and from the 29th to the 1st in a leap February. It also knows the leap year, which most models show with an indicator on the dial.

The program is correct until the year 2100. That year is not a leap year under the Gregorian calendar, because century years are leap years only when divisible by 400, and a mechanical program built around a four-year cycle needs a one-day manual correction then. Nobody buying a watch today needs to worry about that, but it is the reason a perpetual calendar is called perpetual and not everlasting.

The moon phase display works on gearing rather than on the calendar program. A simple 59-tooth moon disc advances one tooth a day and assumes a 29.5-day lunar month, so it drifts by about a day every two and a half years. Astronomical moon-phase mechanisms use gearing that follows the true lunar cycle much more closely, and drift far less. Ask which the specific reference uses, and check the moon against the sky, because a moon that has drifted is an easy correction and does not indicate a fault.

Which Audemars Piguet perpetual calendar references matter?

The 41 mm generation was introduced around 2015 with a new self-winding movement, the calibre 5134, which replaced the ultra-thin base that Audemars Piguet had used in its Royal Oak perpetual calendars for many years. AP's own collection pages list the current Royal Oak references, and they are the place to confirm what is in production today; the Audemars Piguet Royal Oak collection page is a starting point. Reference numbers change with material, dial and edition, so match the reference on the papers with the case back before you buy.

Why is the Royal Oak Perpetual Calendar unusual?

The Royal Oak was designed by Gerald Genta in 1972 as a luxury sports watch in steel, with an octagonal bezel and visible screws, and putting a perpetual calendar inside it was a challenge because the movement has to be slim enough to keep the watch wearable. Audemars Piguet has a long record of thin movements, and the perpetual calendar in a Royal Oak case stays comparatively slim, at roughly 9.5 mm thick according to the specifications we have seen, which is slimmer than most perpetual calendars in sports cases. Confirm the thickness for the specific reference on AP's page.

The dial is the other distinctive feature. Royal Oak perpetual calendars use Audemars Piguet's tapisserie pattern, the fine square grid on the dial, with sub-dials for the calendar indications set into it. The layout is dense but readable, and the layout of the indications differs between references, so study the dial of the specific watch before you buy.

Audemars Piguet vs Patek Philippe perpetual calendar: which one?

The choice is largely about which case you prefer, because both are mechanically serious. Our Nautilus 5740 guide covers the Patek Philippe side of the comparison, and the Nautilus 5726 guide covers the annual calendar, a simpler alternative that only needs correcting once a year, at the end of February.

How is an Audemars Piguet perpetual calendar serviced?

Service is the main cost of ownership. A perpetual calendar has many more parts than a time-only watch and the calendar work has to be reassembled and timed by a watchmaker with experience of the calibre. Audemars Piguet describes its after-sales service on its service page, and the company is the safest place to have a perpetual calendar serviced, because it holds the parts and the specifications for every reference. Ask AP or an authorised service centre for a written estimate for the exact watch, and do not rely on a general figure.

Many manufacturers suggest servicing a mechanical watch every eight to ten years or so, but the right interval depends on the calibre and on how the watch is worn, so follow Audemars Piguet's own guidance for the reference in question. Two habits protect the calendar in between. Avoid changing the date or the day in the hours around midnight, when the calendar mechanism is engaged, unless the owner's manual for the calibre says it is safe. And if the watch stops, reset the calendar and the moon phase in the order the manual gives, rather than turning the crown forward until the display looks right.

How much is an Audemars Piguet perpetual calendar in 2026?

These are the catalogue's dated listings, not quotes, and they will move with condition, papers and demand. The spread is large, and it does not simply follow the metal: the pre-owned steel limited edition is listed above the platinum one, and the ceramic 26579CE is listed well above the steel 26574. Limited editions, materials and condition each move the ask. Audemars Piguet does not publish list prices on its collection pages in every market, so ask an authorised retailer for a current retail figure. Our Audemars Piguet price guide explains how to read these ranges, and auction results at Phillips watches and Sotheby's watches show how the market prices perpetual calendars.

Is an Audemars Piguet perpetual calendar a good investment?

Treat it as a watch to wear first. Royal Oak perpetual calendars have been among the most sought-after complications in modern watchmaking, but no reference is guaranteed to rise, and asking prices can fall when demand cools. A complication also carries a service bill that a simple watch does not, and that cost belongs in the calculation. The features that support value over time are a complete set, an unpolished case, original bracelet links and a service history that shows the calendar has been kept in working order. If resale matters, ask for a written cash-buy assessment before you commit.

Buying an Audemars Piguet perpetual calendar: what to check

• Reference and papers. The reference on the certificate should match the case back, and the serial should match the papers. Our Royal Oak authentication guide explains what to check.
• Calendar function. Ask for a video showing the day, date, month and moon phase and, if possible, the changeover at the end of a month. The indications should agree with each other.
• Moon phase. Compare the display with the actual moon. A small drift is normal; a large one suggests the watch has been stopped for a long time.
• Case and bracelet. Look for polishing that has softened the bevels and for stretch in the bracelet, and ask whether the original links are present.
• Service history. Ask for the record of any service and for the date of the last one. A perpetual calendar with no service record is a larger risk than a time-only watch.
• Authenticity. Buy from a seller that will put an authenticity guarantee in writing; ours is set out on the authenticity guarantee page.

Quick answers

What is an Audemars Piguet perpetual calendar?

It is a mechanical watch that shows the day, date, month and moon phase and accounts for month lengths and leap years automatically, with the Royal Oak Perpetual Calendar 26574 as the core reference.

How often does a perpetual calendar need adjusting?

If it runs continuously, the calendar is correct until the year 2100, when a one-day manual correction is needed. If it stops, it needs to be reset, and the moon phase may need small corrections over the years.

How big is the Royal Oak Perpetual Calendar 26574?

The case is 41 mm in diameter, and it is available in steel, gold and other materials, with the ceramic version listed as the 26579CE.

How much is an Audemars Piguet perpetual calendar?

On September 29, 2026 Bizak's sourced catalogue listed the steel 26574ST at US$120,974 and the rose gold 26574OR at US$140,650, both sourced to order. These are dated listings, not quotes.

How do you service an Audemars Piguet perpetual calendar?

Send it to Audemars Piguet or an authorised service centre and ask for a written estimate. Follow the interval that AP recommends for the reference, and avoid changing the calendar around midnight.

Request an Audemars Piguet perpetual calendar sourcing quote

Tell us the reference or material you want, whether the certificate and box are required, your budget and your timing through our sourcing enquiry form. We confirm the specific watch, photographs, papers and final price before you commit. Catalogue entries: 26574ST steel, 26574OR rose gold and 26579CE ceramic; browse the Royal Oak collection, all Audemars Piguet, or sell or trade your Audemars Piguet.

Related reading: Audemars Piguet price guide · Royal Oak authentication guide · Nautilus 5740 guide · Nautilus 5726 guide.