Horology (from Greek: ὥρα, “hour, time” and Greek: λόγος, logos, “study, speech”; lit. the study of time) is the art or science of measuring time. Clocks, watches, clockwork, sundials, clepsydras, timers, time recorders and marine chronometers are all examples of instruments used to measure time.
People interested in horology are called horologists. That term is used both by people who deal professionally with timekeeping apparatus (watchmakers, clockmakers), as well as aficionados and scholars of horology. Horology and horologists have numerous organizations, both professional associations and more scholarly societies.
Horology has a long history and there are many museums and several specialized libraries devoted to the subject. An example is the Royal Greenwich Observatory, which is also the source of the Prime Meridian (longitude 0° 0′ 0″), and the home of the first marine timekeepers accurate enough to determine longitude (made by John Harrison). Other horological museums in the London area include the Clockmakers’ Museum, and the horological collections at the British Museum, the Science Museum (London) and at the Wallace Collection.
One of the more comprehensive museums dedicated to horology is the Musée international d’horlogerie in La Chaux-de-Fonds (Switzerland). The Musée d’Horlogerie du Locle is a bit smaller but located nearby. One of the better horological museums in Germany is the Deutsches Uhrenmuseum. The two leading specialised horological museums in North America are the National Watch and Clock Museum in Columbia, Pennsylvania, and the American Clock and Watch Museum in Bristol, Connecticut.
Besides museums dedicated only to horology you will often find horological objects in major art museums (including the Metropolitan Museum in New York or the Getty Museum in Los Angeles) or in major museums dealing with the history of science or the history of technology (including the Deutsches Museum in Munich, the London Science Museum or the Musée des Arts et Métiers in Paris.)
One of the most comprehensive horological libraries open to the public is the National Watch and Clock Library in Columbia, PA (USA). Other good horological libraries providing public access are at the Musée international d’horlogerie in Switzerland, at the Deutsches Uhrenmuseum in Germany, and at the Guildhall Library in London.