| 1905 | First radio time signal broadcast from the Navy Yard at Boston, Massachusetts. |
| 1918 | American Henry E Warren patents the first synchronous electric clock. |
| 1920 | M T Favre-Bulle invents the electric clock which bears his name, the Bulle. |
| 1921 | First free-pendulum clock devised by William Hamilton Shortt (1882-1971), is installed
at Edinburgh Observatory. |
| 1929 | Dr Warren A Marrison develops quartz clock |
| 1936 | Speaking clock introduced on British telephone network. |
| 1943 | National Association of Watch and Clock Collectors is organised in Philadelphia |
| 1949 | First atomic clock built |
| 1957 | First battery-powered balance-wheel wristwatch introduced by Hamilton. |
| 1959 | Accutron introduce electric watch with balance-wheel replaced by tuning fork |
| late 1960s | Quartz techology introduced to domestic clocks and watches. |
| 1960s | Floating balance introduced to reduce friction between the balance pivots and their
bushes. |
| 1976 | Great clock of Westminster, 'Big Ben', fails and breaks up inside the clock tower (5th
August) |
