Chronometry

Not to be confused with Chronology.

The hourglass is often used as a symbol representing the passage of time
Clocks; a watch-maker seated at his workbench

Chronometry[a] or horology[b] (lit. 'the study of time') is the science studying the measurement of time and timekeeping.[3] Chronometry enables the establishment of standard measurements of time, which have applications in a broad range of social and scientific areas. Horology usually refers specifically to the study of mechanical timekeeping devices, while chronometry is broader in scope, also including biological behaviours with respect to time (biochronometry), as well as the dating of geological material (geochronometry).

Horology is commonly used specifically with reference to the mechanical instruments created to keep time: clocks, watches, clockwork, sundials, hourglasses, clepsydras, timers, time recorders, marine chronometers, and atomic clocks 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 apparatuses, as well as enthusiasts and scholars of horology. Horology and horologists have numerous organizations, both professional associations and more scholarly societies. The largest horological membership organisation globally is the NAWCC, the National Association of Watch and Clock Collectors, which is US based, but also has local chapters elsewhere.

Records of timekeeping are attested during the Paleolithic, in the form of inscriptions made to mark the passing of lunar cycles and measure years. Written calendars were then invented, followed by mechanical devices. The highest levels of precision are presently achieved by atomic clocks, which are used to track the international standard second.[4][5]


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  1. ^ Harper, Douglas. "horology". Online Etymology Dictionary.
  2. ^ ὡρολόγιον, ὥρα. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
  3. ^ Webster's Dictionary, 1913
  4. ^ Lombardi, M. A.; Heavner, T.P.; Jefferts, S. R. (2007). "NIST Primary Frequency Standards and the Realization of the SI Second". NCSLI Measure. 2 (4). NCSL International: 74–89. doi:10.1080/19315775.2007.11721402. S2CID 114607028.
  5. ^ Ramsey, N. F. (2005). "History of Early Atomic Clocks". Metrologia. 42 (3). IOP Publishing: S1–S3. Bibcode:2005Metro..42S...1R. doi:10.1088/0026-1394/42/3/S01. S2CID 122631200.