In the early 1980s, IWC’s head-watchmaker Kurt Klaus set out on an engineering journey to translate the Gregorian calendar with its many irregularities into a mechanical program for a wristwatch. His ingenious perpetual calendar, which debuted in the Da Vinci Perpetual Calendar in 1985, comprises only about 80 parts and displays the date, day, month, year in four digits, and the moon phase. The smart mechanical program automatically recognises the different length of the months, and even adds a leap day at the end of February every four years.