The concept of an ultra-thin, automatic perpetual calendar seems like an obvious one in classic watchmaking – pairing one of the most prestigious complications with a convenient winding system and a slim, discrete profile. However, it would take the complete disruption of the industry, with the advent of the Quartz Crisis, for it to appear. Once the first one was released, it spawned an entire category, which feels distinctly its own.

Arguably, quite a few models could fall under this category. However, for the purpose of this article, we’ll focus on those which we consider having the most far-reaching legacy, namely the ones created by the ‘Holy Trinity’ brands. Within the span of seven years, between 1978 and 1985, Audemars Piguet, Vacheron Constantin, and Patek Philippe all introduced their own ultra-thin, automatic perpetual calendars – the references 5548, 43031, and 3940. These were amongst the first perpetual calendars to be produced in a series, marking a fundamental departure from the past, when each of these manufactures would only have produced a few dozen of these pieces a year, at the very most. It demonstrated a renewed faith in the future of complicated horology in the wake of an existential crisis.

All three of these watches share key characteristics, not only in their physical form, but in how they were first conceived and how they are collected today. However, what is perhaps the most interesting is how they differ. For example, whilst Audemars Piguet experimented wildly with the design of the complication, Patek Philippe saw itself as the purveyor of classic, restrained aesthetics. From varying dial layouts to different approaches in movement construction, there are some key differences that give all of them their own distinct appeal. Leaning on our own experiences handling and researching these pieces, as well as information from the archive departments at Audemars Piguet and Vacheron Constantin, we thought we’d take a closer look at the battle between these ultra-thin, automatic perpetual calendars.

The perpetual calendar has long fascinated watchmakers. Since the very first one