A new model within the Classique series of Breguet: the Breguet Classique 7327 Quantième Perpétuel
The moon phase or lunar phase is the shape of the sunlit portion of the Moon when you look at it from Earth. These phases change cyclically as the Moon orbits the Earth, according to the changing positions of the Moon and Sun relative to the Earth. The Moon’s rotation is tidally locked by the Earth’s gravity, therefore the same lunar surface always faces Earth. This face is variously sunlit depending on the position of the Moon in its orbit. There are four principal lunar phases: new moon (0% sunlit), first quarter, full moon (100% sunlit), and third quarter (also known as last quarter).
The average calendar month, which is 1⁄12 of a tropical year, is about 30.44 days, while the Moon’s phase (synodic) cycle repeats on average every 29.53 days. Therefore, the timing of the Moon’s phases shifts by an average of almost one day for each successive month. (Lunar year=354 days.) The approximate moon phase can be calculated for any date by calculating the number of days since a known new moon (such as January 1, 1900 or August 11, 1999) and reducing this modulo 29.530588853 (the length of a synodic month). Can you imagine how watch makers manage to create a moon phase complication?
Watches with moon phase
What you can do with a Patrimony is also possible with an Overseas: here is the Vacheron Constantin Overseas Moon Phase Retrograde Date
The Vacheron Constantin Les Cabinotiers Dual Moon Grand Complication is a one-off with 11 complications
The Piaget Polo Perpetual Calendar Ultra-Thin in steel is the latest offspring of the Polo series with moon phase and perpetual calendar
The new IWC Portofino Hand-Wound Moon Phase comes in gold or stainless steel, with a slate dial or a silver-plated dial
The Vacheron Constantin Historiques Triple Calendrier 1948 looks like the Historiques 1942 but now with moon phase
The Ulysse Nardin Executive Moonstruck Worldtimer shows the time and movements of the Moon and Sun in relation to the Earth
The Urban Jürgensen Reference 1741 uses their P4 caliber as base movement; a perpetual calendar with leap year and moon phase is added
The A. Lange & Söhne 1815 Rattrapante Perpetual Calendar Handwerkskunst is yet another technical showcase by Lange
A mouth full: the Bovet Récital 20 Astérium 10-day Flying Tourbillon Night Sky Annual Calendar with Astronomical Functions