Audemars Piguet Quantième Perpétuel Automatique Squelette

What is a Perpetual Calendar? 

Why do we have leap years? Leap years exist because the true solar year is approximately 365.24 days, which is slightly longer than our typical 365-day a year calendar. Therefore, to make up for the variance, we add an extra day (February 29th) every four years. However, to complicate matters, adding the leap day makes the calendar longer. To recalibrate, leap years have to be omitted every so often and the next time a leap year will be skipped will be the year 2100.

If we consider how our calendar is structured (where days of the month not only vary between 28 to 31 days, but every four years we also have to account for an extra day) we can start to appreciate how incredible a mechanical perpetual calendar watch is.

Perpetual calendar watches display the day, date, and month (and frequently the moon phases too) while keeping track of leap years. As a result, a perpetual calendar can indicate the correct date without the need for adjustments in perpetuity — well, at least until March 1, 2100. 

The Audemars Piguet Perpetual Calendar 25668

In 1978, at the height of the Quartz Crisis, Audemars Piguet audaciously launched an ultra-slim automatic perpetual calendar in the form of the Reference 5548. Many have credited this risky approach as having saved the company during an era where the quartz trend decimated the Swiss watch industry. Inside the AP Perpetual Calendar Reference 5548 was the super slim Caliber 2120/2800, which merged a Jaeger-LeCoultre base movement with a Dubois Dépraz perpetual calendar module. This movement proved to be a cornerstone of the AP Perpetual Calendar lineup and was used across 70 different references.   

One of these references is Ref. 25668, also known as the Audemars Piguet Perpetual Calendar Automatic Skeleton, pictured here. These openworked Perpetual Calendar models were made from 1988 to 1993 specifically to show the beauty of the self-winding caliber inside the watch — from both the dial side and the caseback. The openwork design illustrates the incredible craftsmanship that goes into hand-finishing each movement, from engraving and beveling to polishing and flanking.  

Audemars Piguet only made 205 examples of the self-winding Perpetual Calendar ref. 25668, available in four different metals: 94 in yellow gold, 79 in platinum, 30 in pink gold, and two in white gold. Despite the complicated nature of the watch, the case of Reference 25668 measures a restrained and elegant 36mm in diameter and a mere 7.5mm thick. 

The openworked (or skeletonized) dial of the Audemars Piguet Perpetual Calendar 25668 is beautifully designed, with four subdials that serve to display the perpetual calendar. There’s the date at 3 o’clock, the moon phases at 6 o’clock, the day at 9 o’clock, and the month at 12 o’clock, all of which float above the visible movement. 

Made for the Fine Timepiece Connoisseur 

Though Audemars Piguet is best known today for its immensely popular Royal Oak watches, fine timepiece connoisseurs understand that the brand’s range of complicated watches is what distinguishes it as a high horology manufacturer.  

Flawlessly designed and built, the Audemars Piguet Quantième Perpétuel Automatique Squelette ref. 25668 is a rare and highly collectible watch for serious collectors. With a little over 200 examples ever made, those who have the privilege of owning an Audemars Piguet Perpetual Calendar 25668 are part of an exclusive club, indeed.