Patek Philippe 5496 PERPETUAL CALENDAR WITH RETROGRADE DATE HAND
A perpetual calendar with a retrograde date hand is a rare combination presented in an unusual layout. Instead of sweeping a full circle, the date hand jumps back to the beginning of its arc 24 hours after having reached the last day of the month. It advances day by day until it indi- cates the 28th, 29th, 30th, or 31st of the month (depending on the current month and leap year cycle) and subsequently returns to the 1st day of the month. A spiral spring is used to perform this instant retrograde motion of the date hand. The ingenious mechanism developed by Patek Philippe does not absorb any energy from the mainspring barrel and prevents the date hand from bouncing forward to the 2nd or 3rd day of the month when the retrograde motion takes place. In contrast to other Patek Philippe watches with perpetual calendars, the perpetual calendar with a retrograde date hand is based on the self-winding caliber 324 movement with a central rotor. This ranks it among the rare perpetual calendars with a sweep seconds hand. The moon phase display is extremely accurate and deviates from the true lunar cycle by only 11 min- utes and 47 seconds per year. The deviation adds up to merely one day in 122 years and 45 days. If the watch is worn daily, the per- petual calendar will not have to be corrected until February 28, 2100. This is a so-called secular year that, as an exception, omits February 29.
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