Audemars Piguet Perpetual Calendar

Audemars Piguet's Royal Oak Perpetual Calendar, reference 26579CB.OO.1225CB.01, has a 41 mm white ceramic case. The case measures 9.5 mm thick and the dial sits behind a sapphire crystal. Inside is the self-winding calibre 5134, an in-house movement built for perpetual calendar work. The blue dial shows date, weekday and month alongside a moon phase display, all coordinated so the calendar tracks the length of each month without manual correction. This combination of functions places it among the more complicated pieces in the Royal Oak line. The bracelet is made of the same white ceramic as the case and closes with a folding clasp. Water resistance is modest at 20 metres, in keeping with a dress-oriented perpetual calendar rather than a sports watch.