Just looking at a picture of the Rotonde de Cartier Day and Night, you might think it is a more traditional moon phase watch, but you would be mistaken. In fact, the dial is split between upper and lower halves, with the lower portion showing the phases of the moon via a retrograde hand, as is clearly shown in the picture.

In the upper half, time itself is split into day and night, hence the name of the watch, by way of a disc that makes a complete circuit every 24 hours; only the top part of the disc is exposed, with the hours during the day marked by a symbol for the sun and night time hours marked by a stylised moon. According to Cartier, this day/night indicator is amongst the largest ever made.

Longtime followers of Cartier watchmaking might recall a movement similar to the automatic calibre 9912 MC at work here. Minus the retrograde moon phase, there was once a Collection Privée watch with much the same characteristics, powered by calibre 9903. Unlike that watch, where the minutes were in retrograde form, the new Rotonde de Cartier Day and Night shows the minutes conventionally.

With a diameter of 43.5mm, the watch is available in 18K pink gold and, remarkably, in palladium. Neither version is limited (prices on application).