... A clock is a tool for the time counting. The stable repeating processes are used in clocks. ... The first timepieces were sand glasses; in the 2nd thousand years B.C. there occured water clocks; the first mentions about mechanical timepieces related to the end of the 6th century; the modern mechanical timepieces are created by H. Huigens in 1657; in 70th years of the 20th century there were widespread the electronic quartz watches with numeric indication, for example on the liquid chips. ...