A watch is a timepiece, typically worn either around the wrist or attached on a chain and carried in a pocket. Wristwatches are the most common type of watch used today. Watches evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were strictly mechanical. As technology progressed, the mechanisms used to measure time have, in some cases, been replaced by use of quartz vibrations or electronic pulses. The first digital electronic watch was developed in 1970. Before wristwatches became popular in the 1920s, most watches were pocket watches, which often had covers and were carried in a pocket and attached to a watch chain or watch fob.