Perpetual calendars come in all forms, shapes, metals, and prices. However, few brands stand out from the rest as far as their perpetual calendars in terms of history, reliability, and prestige. When you are looking for a perpetual calendar the first brand names that pop up would be Patek Philippe, Audemars Piguet, and Vacheron Constantin as these make the ‘holy trinity of watchmaking’. Audemars Piguet has a long history making perpetual calendars and after the successful release of the Royal Oak Perpetual ref. 26574 at the end of 2015, the brand pushed the envelope even further in 2018 presenting a prototype of what would become the world’s thinnest automatic perpetual calendar.