Tools for knowing time have existed since ancient times. Historical evidence tells us that the first to divide the day into smaller units were the Egyptians. Studying the movement of certain stars that were associated with various divinities, they divided the night into 12 parts. They later built the sundial around 3,500 BC, which was based on the obelisk. A certain moment of the day was determined by the way the shadows cast by the Sun moved on the ground.
Already four millennia ago, the Babylonians, in the epic poem Enuma Eliș, presented a calendar model made up of 12 months of 30 days each. This way of measuring time corresponded to their sexagesimal counting system, which later turned into the duodecimal (which would later be used to number the hours).
Defining the calendar does not completely solve the problem of measuring time. The first to divide the day into smaller units were the Egyptians. Based on religious reasons, around 2100 BC. they divided the night into 12 parts by studying the apparent movement of the stars which were mostly associated with various divinities.
A first episode in the evolution of clocks were – Water clocks invented by the Greeks
Because the sundials of the Egyptians had limited possibilities of use, the Greeks invented the water clock, which could also be used indoors at night or when the sky was not completely clear. However, even the clock of the Greeks was far from perfect, not being as accurate as the sundial.
In Greece, water clocks were used to measure and limit the pleading time of lawyers during trials. In this way, the people responsible for the water clocks began to be bribed. They filled only a small part of the watch with water for the plea of their rivals, their time to plead their case being thus shorter and their chances of winning smaller.
In the history of the water clock invented by the Greeks, however, the alarm clock also has its origin. The Greek philosopher Plato is said to have had a water clock with an alarm whose sound was similar to the sound of a water organ. He was preparing the evening watch to be woken up in the morning, when the classes had to start.