Ancient Egyptians were concerned with the annual cycle of the seasons to establish the time for cultivating and harvesting.
For certain individuals, however, time was extremely important; these were the astronomers and priests who were responsible for determining the exact hour for the daily rituals and for the important religious festivals. Sundials, which allowed the astronomers and priests to observe the passing of the 12 daylight hours, could not be used to record the 12 nighttime hours.
A man called Amenemhat created the first water clock in the time of Amenhotep the First. The water clock enabled the Ancient Egyptians to measure the passing of every 12 hours, both night and day, winter and summer.