A clock is an instrument to measure, keep, and indicate time.

The evolution of the technology of clocks continues today. The apparent position of the Sun in the sky moves over the course of each day, reflecting the rotation of the Earth.

Shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day.

Given their great antiquity, where and when they first existed is not known and perhaps unknowable.

The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC.

During the 15th and 16th centuries, clockmaking flourished.

The next development in accuracy occurred after 1656 with the invention of the pendulum clock.

The Greek and Roman civilizations are credited for initially advancing water clock design to include complex gearing, which was connected to fanciful automata and also resulted in improved accuracy.

These advances were passed on through Byzantium and Islamic times, eventually making their way back to Europe.

Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain.