Perpetual calendar
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A perpetual calendar is a calendar valid for many years, usually designed to look up the day of the week for a given date in the past or future.
Illustration from 1881 U.S. Patent 248872, for a perpetual calendar paperweight. The upper section is rotated to reveal one of seven lists of years (splitting leap years) for which the seven calendars below apply.
A 50-year "pocket calendar" that is adjusted by turning the dial to place the name of the month under the current year. One can then deduce the day of the week or the date.
Breguet classique Grand complication perpetual calendar
Perpetual calendar wristwatch by Patek Philippe
Vacheron Constantin
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Vacheron Constantin SA is a Swiss luxury watch and clock manufacturer founded in 1755. Since 1996, it has been a subsidiary of the Swiss Richemont Group. Vacheron Constantin is the oldest continuously
François Constantin
Advertisement from 1896 promoting their observatory trial results
Vacheron Constantin shop in Manhattan
A Vacheron Constantin pocket watch in Metropolitan Museum of Art, New York