Huygens invents pendulum clock In 1656, Christiaan Huygens completed his design of the first ever pendulum clock and hired Dutch clockmaker Salomon Coster to build it. In a letter he wrote to Ismaël Boullian, Huygens dated his invention to 25 December 1656. In another letter, this time to Jean Chapelain on 28 March 1658, Huygens describes taking a horizontal table clock and adapting the escapement for a pendulum, thus providing the first known written description of a pendulum clock. With this invention, Huygens achieved unprecedented accuracy in the measurement of time, and his domestic pendulum clock design was truly a horological breakthrough.
