Perpetual calendar with digital date and month displays
Despite the complexity of the perpetual calendar with four large discs for the date and month, as well as a small leap year disc, it can be easily set using the crown and will not require correction until 2100. The date advance wheel for the single-digit and tens discs advances daily. However, the quick-action switch siphons off a little energy every night when the date display moves forward. It stores this energy and then discharges it precisely at the end of the month or year when, in addition to the date and month disc, the leap year disc also needs to be advanced. The digital display dates back to the IWC Pallweber watches from 1884 that displayed the hours and minutes using digits.