There are many ways to display time on a watch. The most common one by a distance is using two central hands, an hour and a minute hand.
However, we also know Regulators, Retrograde hands or very common for digital watches a decimal number display.
The classic central two hands suffer from one disadvantage, you cannot tell the difference between AM and PM, between morning or afternoon hours, day and night. Some watches solve that by adding a small 24 hour dial or a GMT Hand and some like Lange went through great effort in displaying a digital clock on a mechanical wristwatch as in the Zeitwerk.
Another good option is to use a mix of a central minute hand and some sort of hour display, like a jumping hour, digitally displayed.
I freely admit, I’m not a fan of digital displays when it comes to time.
Girard-Perregaux found its own, quite unique way to display Day and Night through a rotating 24 hour disc. The technology behind this is known from World Timers, but here we do not have timezones and display only time with the addition of a Small Seconds and Power Reserve indicator.
The Girard-Perregaux Richeville Day/Night has its distinctive tonneau case as typical for the modern Richeville line. All hands and indicators are blued and the large minute hand is simply gorgeous with its large blue arrow and its quite massive counter-weight.
Each display has its own unique hand shape, something GP has been doing on quite a few watches.
So in order to read time, you will read the hour above the top blue arrow indicator from the counter-clockwise rotating disc and of course, the minutes from the minute hand as usual. It is not as intuitive as the classic two-hander solution and it takes some time to get used to. Reading the hour can also be tricky at times as the numbers are quite small or if the light is low. The colouring of the day versus the night hours dividing the ring into Day and Night however does help. Every index represents an advance of 2 hours, so for example if you can see the shift from Day to Night at the 1 index, you know it is 4pm. You’ll get used to telling time like that very quickly.
The Richeville Day and Night is quite a rare GP that even among GP enthusiasts you do not see this watch very often. It was available in Steel and Pink Gold and produced in the late 2000s.
Girard-Perregaux Richeville Day/Night
Caliber GP 033G0
Case: 37mm x 37mm Steel Tonneau