A paragon of visual balance and legibility, the perpetual calendar model bearing Reference 5320 was designed in 2017 in a white gold case with a cream-lacquered dial. Its vintage style is reinterpreted in a new white gold version fitted with a gilded opaline rose gold dial. The calendar displays are arranged in the characteristic manner of Patek Philippe perpetual calendar watches since 1941, with a twin in-line day/month aperture at 12 o’clock and a date indicated by a hand surrounding a moon-phase aperture at 6 o’clock. These are complemented by two round apertures: one for the day/night indication between 7 and 8 o’clock; and the other for the leap-year cycle between 4 and 5 o’clock — both of which are useful to adjust the calendar. The extremely accurate moon phases require a one-day correction only once every 122 years.