In the 1300's the mechanical clock was born. With the newly invented clock time was measured in 24 hours. When the famous scientist, Galileo, invented the pendulum in 1581 it improved the movement of the " hands " of a clock. With the pendulum the clocks varied by a few seconds, without it, it varied from 10 to 15 minutes. Then later on in the 1600's gears, wheels, and screws were used in the making.