Audemars Piguet Platinum Perpetual Equation of Time Ltd

Audemars Piguet Platinum Perpetual Calendar Limited Edition - Automatic winding; 41 jewels. Platinum case, polished bezel calibrated for equation time and London latitude of 12h00' ( 39 mm ) Comes with 4 different bezels; Geneve, Roma, Singapore, Moskow. Silver engine turn dial with applied baton numerals; four subsidiary dials for day combined with date, month with aperture for moon-phases, sunrise and sunset, outer track calibrated for equation of time indicated by a central serpentine hand. Black Audemars Piguet strap with Platinum Audemars Piguet buckle. Pre-owned with Audemars Piguet box. Circa 2007. Limited Edition The 'Equation of Time' shows the difference between 'Apparent Solar Time' and 'Mean Solar Time', which is the variable time shown by a sundial, and 'Mean Solar Time', which is the constant, civil time shown on a watch. Because of earth's elliptical orbit (the earth actually rotates around the sun irregularly), the 'Equation of Time' therefore varies from approximately plus 14 minutes (the greatest positive value) around 12 February, to approximately minus 16 minutes (the greatest negative value) around 3 November. It is understood that 'Apparent Solar Time' and 'Mean Solar Time' only precisely match each other 4 times a year, on or about 16 April, 14 June, 1 September and 25 December (while the 'Equation of Time' is zero).