An annual calendar complication is one of the most useful functions on a watch and only needs adjusting once a year as February leads into March. In true Cartier style, this Rotonde de Cartier model features an ingenious way of displaying the information, with the days of the week featured on the periphery in apertures cut into the dial, the date at 12 o’clock and the months in a small aperture just above six o’clock. The 40mm pink gold case flaunts the hallmark Cartier blue cabochon sapphire in the crown, which in turn is the command centre for adjusting all the functions. The large Roman numerals are also très Cartier, as is the central sunray guilloché finish and blue steeled hands. For horophiles, the automatic manufacture movement - calibre 9908 MC - is revealed through the sapphire crystal caseback and will keep the watch in perfect time for 48 hours.