Based upon the caliber 1150, the movement of the Day Night is larger in diameter. The winding rotor, decoratively engraved and polished, has been enlarged to enhance the view of the movement through the sapphire case back. The timepiece comes in a 40 mm 18ct red gold case, 12 mm thick. The bezel is set with two spiral shaped rows of 140 diamonds.
The dial is fashioned entirely in mother of pearl and is divided into three parts on four levels, thus creating an impression of great depth.
The day/night disk turns twice per day. Each rotational change takes place over approximately four minutes, as the decoration presents itself, allowing the discovery of all of the details of the disk. Many different artistic techniques were used in its creation: la décalque, le champlevé), and le marquetage. Gradations in the color blue, achieved by deposit upon the mother of pearl, marks the change from day to night. The moon is composed of 50 diamonds; the sun of 50 yellow sapphires. Placed upon the surface are several yellow colored mother of pearl dots as well as 14 diamonds which represent the stars.
The two retrograde indications (seconds and hours) are combined with the minute hand. The minute is displayed with a regulator hand which continuously sweeps over its circle of rotation. As it completes its 60 minute march, the seconds hand is retrograding, which is to say that it has progressed along its arc and returns instantly to its point of departure to begin anew its progression. Similarly, the hour hand retrogrades twice per day, again in synch with the minute hand.
Blancpain has perfected the design of retrograde indications. Based upon snail shaped cams, Blancpain’s design ensures smooth movement of the hands along the arc of travel and a positive, swift, yet vibration free return to the starting point. The gear train of the Day Night disk is secured, meaning that it can be set at any time of day.
The setting of the time and the disk are independent. The setting of hours and minutes by the crown, through a lever, disconnects the indication from the running train of the watch.
The Day Night is fitted with a white ostrich strap.