What is a Perpetual Calendar watch and how does it work?
The early “calendar” watches, dating from the 16th century, were equipped with a mechanism giving the day, date and month in addition to the hour which was still imprecise at that point in time. In a calendar watch, the days and months follow sequentially but the same cannot be said of the dates which are either 28, 29, 30 or 31 depending on the month and whether it is leap year or not. In a “simple” calendar watch, it is necessary to correct the date five times during the year, i.e. the ist day of March, May, July, October and December Abrahain-Louis Breguet is usually credited with having invented the mechanism which made these corrections automatically. His invention led to today’s “perpetual calendar” watches as opposed to “simple calendar” timepieces. These models are based on the Julian calendar rather than the Gregorian calendar in use today. As a result, leap years are not deleted at the end of three out of four centuries, thus making it necessary to correct the watch three tim
