In early 1990s, the Swiss watch industry was slowly recovering from the Quartz Crisis, Philippe Stern, then president of Patek Philippe, wanted to bridge the gap between the relatively straightforward complete calendar, and the highly complicated perpetual calendar.
Through creative collaboration between Patek Phillipe's design and engineering department and final-year students at the Geneva School of Engineering, the Annual Calendar complication was born. Patented by Patek, this new type of movement utilises two finger pieces set at an angle to one another. The first advances the date wheel once a day. For the months of April, June, September, and November, the second finger comes into play, advancing the date wheel from 30 to 1, skipping the 31st day. Therefore, one will only need to adjust the watch at the end of February.
It is also interesting to note that while the Annual Calendar is simpler than a perpetual calendar by design, the movement 324 S IRM QA LU in the 5146 actually has more parts than Patek's Perpetual Calendar movement 240 Q. Combining with the power reserve at 12 o’clock, the 5146 has two of the most useful complications to make it a versatile daily wearer.
Case: 18K White Gold
Case Size: 39
Caliber: 324 S IRM QA LU
Strap: Patek Philippe Brown Strap with 18k White Gold Patek Philippe Deployant Clasp.
Full set with its inner and outer box, manuals, date corrector pusher and guarantee certificate.
With 18k White Gold Patek Philippe Deployant Clasp