On the annual calendar, the month, date and day are displayed in three separate windows arranged according to the American date format. The complication automatically takes into account the differing lengths of individual months. In contrast to the perpetual calendar, the date on this model needs to be advanced manually via the crown once a year at the end of February. Two barrels provide enough torque to drive the three display discs. Overall, it took IWC’s watch designers 5 years to develop the annual calendar.