Timeline of time measurement technology

• 270 BC - Ctesibius builds a popular water clock
• 46 BC - Julius Caesar and Sosigenes develop a solar calendar with leap years
• 1000s - Sets of hourglasses were maintained by ship's pages to mark the progress of a ship during its voyage
• 1000s - Large town clocks were used in Europe to display local time, maintained by hand
• 1335 - First known mechanical clock, in Milan
• 1502 - Peter Henlein builds the first pocketwatch
• 1582 - Pope Gregory XIII, Aloysius Lilius, and Christopher Clavius introduce a Gregorian calendar with an improved leap year system
• 1655 - Cassini builds the heliometer of San Petronio in Bologna, to standardise Solar noon.
• 1656 - Christian Huygens builds the first accurate pendulum clock
• 1676 - Motion works and minute hand introduced by Daniel Quare
• 1680 - Second hand introduced
• 1737 - John Harrison presents the first stable nautical chronometer, thereby allowing for precise longitude determination while at sea
• 1850 - Aaron Lufkin Dennison starts in Roxbury, Mass.U.S.A. the Waltham Watch Company and develops the American System of Watch Manufacturing.
• 1884 - International Meridian Conference adopts Greenwich Mean Time for consistency with Nevil Maskelyne's 18th century observations for the Method of Lunar Distances
• 1893 - Introduction by Webb C. Ball of the General Railroad Timepiece Standards in North America: Railroad chronometers
• 1928 - Joseph Horton and Warren Morrison build the first quartz crystal oscillator clock
• 1946 - Felix Bloch and Edward Purcell develop nuclear magnetic resonance
• 1949 - Harold Lyons develops an atomic clock based on the quantum mechanical vibrations of the ammonia molecule
• 2008 - Launch date for the Primary Atomic Reference Clock in Space.

See also: clock