The perpetual calendar, Vacheron Constantin reminds us in the press release for the Traditionelle Twin Beat Perpetual Calendar, is the most “useful” of high complications, but its utility comes with one major drawback. If by chance a perpetual calendar should be allowed to run down, re-setting the indications – which may include the date, as well as the day, month, and year, as well as sometimes the age and phase of the moon, depending on the design – may prove to be something of a challenge; with many traditional designs, performing the operation improperly means the watch must go in for service to be re-set by a watchmaker. (One of the more grim moments in my life as a watch writer was setting a synchronized perpetual calendar which hadn’t run in three years – as all the calendar indications were set from the crown, this meant turning the hands, via the crown, for three years’ worth of 24 hour cycles. This took two days. The fam found it hilarious. There was colorful language.) Vacheron Constantin has come up, in the Traditionelle Twin Beat Perpetual Calendar, with a most intriguing and unusual solution: a watch with a “standby” mode, in which the power reserve is 65 days. Not hours, days – over two months of running time.