A perpetual calendar in an Officer's case with retrograde date is not a new complication from Patek Philippe. Although it must be said that the 5159G-001 is a big technical jump up from earlier references. The 'retrograde' complication allows the date indicator to instantly flick back to the first of the month at midnight on the last day of each month. The perpetual nature of the watch means that it will not require adjusting and will take account of the different number of days in each month when changing date, it even factors in leap years. The moon phase indicator at the 6 o'clock position has been calibrated so that it only requires correction of 1 day every 122 years. The slightly larger 38mm case means the layout is cleaner, the movement can be viewed through the hinged dust cover to the rear. Here in contemporary white gold on a brown alligator strap for a more casual look.