In modern watchmaking, a perpetual calendar displays the date and automatically corrects for months of less than 31 days and for leap years. Unless the movement takes into account non-leap century years, watches equipped with a perpetual calendar require manual adjustment at 2100, 2200, and 2300, but not at 2400. Usually, perpetual calendars incorporate additional complications. 
Patek Philippe’s cushion-shaped perpetual calendar watch, the Ref. 5940 is now also available with a perpetual calendar function. The 5940 is also now available in a pink gold case. It houses Patek Philippe’s ultra-thin Caliber 240 Q micro-automatic movement.
In January 2017, Hermès unveiled a new model of the Slim d’Hermès Quantième Perpétuel with a platinum case and blue dial. The replica watch is powered by in-house Caliber H1950, a super-thin mechanical movement with a micro-rotor.
During SIHH 2017, Audemars Piguet unveiled the Royal Oak Perpetual Calendar with a black ceramic case and bracelet. The 41-mm-large case houses the self-winding Caliber 5134. However, a few years ago, Frederique Constant unveiled to the world the Manufacture Perpetual Calendar with a full, in-house-developed perpetual calendar, priced under $10,000.
The hand-wound Tourbillon Perpetual Calendar in platinum “Pour le Mérite” is A. Lange & Söhne’s most complicated fake watch with the attributes of a “Pour le Mérite”. The in-house movement combines five grand complications: perpetual calendar, chronograph, ratchet function, fusible chain drive, and tourbillon. The large 43mm Perpetual Calendar Tourbillon is limited to 50 pieces and is competitively priced.
