The history of clocks includes timekeeping and sundials established thousands of years ago by ancient civilizations, water clocks in the second century B.C. and the tower clock in the 11th century A.D. Europeans built the first mechanical clock in the 1200s and the first wristwatch in the 1500s.
Humans started keeping time with sun clocks or sundials in 3500 B.C., simple contraptions that used the shadows of stone pillars to tell time. More accurate and precise sundials, called hemispherical dials, were concave shapes cut into the ground. The Greeks built water clocks in 300 B.C., bowls with water that dripped out of a hole in the bottom at a consistent rate. These clocks rang bells or had mechanized whistles and were the first alarm clocks. The Chinese built a water clock tower in 1088 A.D.
History first mentions attempts at making mechanized clocks in 1271; these used turning wheels that caught and turned other knobs with a foliot or pendulum to regulate the movement. The Italians succeeded in creating these large mechanical clocks by the mid-1300s. The Germans invented spring-powered clocks in the early 1500s and portable timepieces, but didn't add minute hands to the clock faces until 1670.
The Dutch invented the pendulum clock in 1656, followed by the modern balance wheel and spring assembly in 1675. Shortt clocks and then quartz crystal clocks succeeded pendulum-based clocks in 1921 and the 1930s respectively. The atomic clock originated in the United States in 1949.