This past March, at Baselworld 2012, Patek Philippe showed off their first ever regulator timepiece, the Ref. 5235 Annual Calendar Regulator. Consisting of a central minute hand, a subsidiary seconds dial (at 6 o'clock) and a subsidiary hour hand at 12 o'clock - the regulator dial separates the different time functions. Regulator timepieces were used historically, to keep time as accurately as possible, specifically at workshops and observatories - where accurate timekeeping was paramount. Furthermore, to animate this all new functionality, Patek Philippe watchmakers created an all new manufacture movement.
"When adjusting their timepieces, watchmakers needed an unobstructed view of the seconds hand, which is why the hour display was moved to an off-center location where it would not sweep over and thus partially cover the seconds dial for several hours in the course of a day. One of the finest examples of this type of freestanding precision clocks is the Patek Philippe & Co. regulator built at the beginning of the last century. For many years it has been keeping the time unperturbed - second by second - in the office of Philippe Stern, the company's honorary president."
The Ref. 5325 features an Annual calendar function, which automatically recognizes 30-day and 31-day months and only needs to corrected once per year. To make the adjustment, corrector buttons are located on the upper left quadrant of the case flank: Date between 9 and 10 o'clock, Month at 10 o'clock, Day at 9 o'clock (comes with correction stylus in ebony and 18K white gold).