Chronology of Time Measurement Technology
| -270 | Ctesibius builds a popular water clock. |
| -46 | Julius Caesar and Sosigenes develop a solar calendar with leap years. |
| 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. |
| 1656 | Christian Huygens builds the first accurate pendulum clock. |
| 1737 | John Harrison presents the first stable nautical chronometer, thereby allowing for precise longitude determination while at sea. |
| 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. |