The Jules Audemars Equation of Time was introduced into the market in 2000. This complicated wristwatch incorporates a perpetual calendar that also mechanically tracks the time of sunrise and sunset for the designated city (indicated on the recessed inner ring following its owner's request). The timepiece also accurately shows the difference between mean solar time and sidereal time. The equation of time is the difference between true solar time and mean time. True solar time, such as shown by sundials, varies daily because of the Earth's elliptical orbit along with the longitude of the point of observation. Mean time, such as shown by watches, ignores these variations, and mathematically equally divides every day of the year into equal hours. The watch consists of 423 components and features a sapphire caseback to view the inhouse movement, representing Audemars Piguet's dedication to the art of fine watchmaking.