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 complex movement through the sapphire case back. With a diameter of 40 mm, this timepiece offers an harmonious balance between its diameter and thickness as its height is less than 12 mm. The dial is fashioned entirely in mother of pearl and is divided into three parts on four levels. The differences in height create an impression of great depth. Careful work was called for to fashion the mother of pearl surface upon progressively descending levels, as the mother of pearl material on a base of German silver becomes progressively thinner with each level and, therefore, more fragile.

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 day and the night. Many different artistic techniques were used in its creation: la décalque (depositing material), le champlevé (contour forms in relief), and le marquetage (integration of superimposed motifs in mother of pearl). 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 is fashioned with 50 yellow sapphires. Placed upon the surface are several yellow colored mother of pearl dots as well as 14 diamonds which represent the stars.

One of the unique features of this piece is the way that 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.

Blancpain’s signature design elements such as the double stepped case with its rounded shoulders are found in this timepiece. The bezel is set with two spiral shaped rows of 140 diamonds around its exterior. The Day Night is fitted with a white ostrich strap.