From Sundials to Watches: The History of Timekeeping

How many times a day do you look at your watch or smartphone to find out what time it is? Keeping time is something that people do every day, but very few people know where timekeeping actually came from. Why do we have 24-hour days? Who decided what increments of time to use? The history of timekeeping goes all the way back to ancient times when the stars and the shadows of the sun were all they had to keep time. These days, the methods used for keeping time are much more advanced, but the principles we use are still thousands of years old.

Watching the Stars

The sexagesimal system of time we use today, which breaks time down into increments of 60 seconds in a minute and 60 minutes in an hour, was first developed 4,000 years ago by the ancient Egyptians and Mesopotamians. It is a system that utilizes the position of the stars, the moon and the sun to keep track of the hours of the day. Ancient structures such as Stonehenge are thought to be early devices to tell time and also act as calendars.


In around 1500 B.C., the ancient Egyptians started to utilize sundials. The concept behind measuring time using the position of the sun and the shadows it creates actually started with the ancient Egyptian obelisks that had first appeared in 3500 B.C. Through the use of a sundial, the ancient Egyptians were able to create a more accurate way to break down each day into 24 segments of one hour each.

  • Sundials - The "Engines of our Ingenuity" series of the University of Houston discusses the history of sundials.
  • Equatorial Sundials - This is a description of how to make and use an equatorial sundial.
  • Making a Sundial (PDF) - This is a very easy to understand description of how to create your own sundial.
  • The Mathematics of Sundials (PDF) - This article explains in great detail how to properly utilize a real sundial.

Water Clocks

Plato is credited with many inventions that have altered the world, but few people realize that this ancient Greek invented the first alarm clock. Plato devised a system that would allow for the predictable flow of water into urns that were filled with metal balls. After filling for several hours, the water would reach the top of the urns at the precise moment that Plato wanted to be awakened. The metal balls would flow from the urns and hit a copper plate, creating a noise that would rouse the ancient inventor. That is how the first alarm clock was invented.

Mechanical Clocks

Clocks with gears and mechanisms actually appeared as early as the 11th century, but they were usually paired up with water clock technology or some other way to move the gears. Winding mechanical clocks started to appear in medieval monasteries because of the strict prayer schedule that the monks needed to keep. Large clock towers started to be erected in monasteries and they were often wound twice a day. From there, other clock makers started to emerge and create huge clock towers around the world.


Mechanical clocks and clock gears led the way for pocket and wrist watches. Robert Hooke invented a device known as the hairspring in 1675, and that opened the door to creating smaller components for watches. The first wrist watch was said to have been given to Queen Elizabeth I of England in 1571, although the accuracy of wrist watches could not be improved until Hooke's 1675 modification.

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