IWC Portugieser Perpetual Calendar Watch, 44.2mm White Dial, IW503302A moon you can rely on, even under cloudy skies: the perpetual calendar's high precision moon phase display needs a one day adjustment every 577. 5 years. The moon phase display on the Portugieser Perpetual Calendar diverges by just 1 day in 577. 5 years from the actual phase of the moon. The elegant timepiece leaves virtually no wish unfulfilled. It is equipped with features such as a perpetual calendar, a window showing the year in four digits and a