Mystery of the 24-Hour Day & Who Made This Rule

Time is the basis of our existence on this planet. It decides our daily schedules, time, and how we look at the world around us. Of these main elements of time, one of the most important is the 24-hour day. You might ask why we only have 24 hours a day, and who created the rule. Today, the system of time appears natural; yet, its origins date back to ancient civilizations, astronomy, and human ingenuity. It emerged from practical needs and cultural developments spanned many thousands of years.

The Origin of 24-Hour In A Day

The 24-hour day was a phenomenon that dates back thousands of years into the ancient past with its origin in Egypt and Mesopotamia. Some 4000 years ago, the 24-hour day was discovered by the ancient Egyptians, where they divided it equally into daylight and nighttime, both being 12 hours long. This division was based on the movement of the sun and stars, which after careful observation, they could find the celestial world.
The Egyptians divided daylight into 12 parts by sundials. At night, they used a group of 36 star groups known as "decals," of which each would rise about every 10 days. Observing 12 of them helped the Egyptians divide the night into 12 hours. Thus, the 24-hour day was born from a combination of 12 daylight hours and 12 nighttime hours.
The Egyptians used the duodecimal, or base-12 system of counting that many ancient cultures did because it was practical. Again, 12 is easily divisible by the numbers 1, 2, 3, 4, and 6; by doubling this to 24, they created a system that allows for finer timekeeping division. This practical base divided the day into 24 hours the logical step in keeping time.
Sumerians and Base-60 System
About the same time that the ancient Sumerians of Mesopotamia began working on their base-60, or sexagesimal, numerical system around 3000 BCE, they also were making great contributions to the history of timekeeping. This was partly because 60 can be so easily divided by all those numbers-including 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, and 30-and because it has many factors, which means it makes fractions and other mathematical calculations relatively simple.
The Sumerians did not invent the 24-hour day, but their mathematics paved the way for future systems. Even now, their influence can be seen in the units of measurement that we use: angles, geography coordinates, and time—60 minutes an hour and 60 seconds a minute.

The Greeks and Romans

The Egyptian system of 24 hours was a refinement made by Greek astronomers and scholars. The Greek astronomer Hipparchus, born around 150 BCE, played a crucial role in adopting and fine-tuning the division of the equinoctial day when day and night are equal into 24 equal parts. That was a great step toward establishing a common division of time for the entire Hellenistic world. His work laid a foundation for later astronomical systems, such as Ptolemy's works, which served as reference texts for later civilizations.
The Romans, who were loaning the 24-hour system they borrowed from the Greeks and the Egyptians, also used sundials and water clocks to measure time. However, as a consequence of daylight changes over a year, hours would vary in length being shorter than others. In winter they were shorter, and in summer longer.
Only with the invention of mechanical clocks during the Middle Ages did equal-length hours over a day and night become standard.

The Mechanical Clock Revolution

For quite a long time, sundials and water clocks were considered the best available tools for measuring time. Although sundials and water clocks were novel at the time, they proved to be imprecise and sensitive to seasonal and local environmental factors such as sunlight and flow rate. This all changed in the 14th century with the discovery of mechanical clocks. Mechanical clocks ushered in a whole new era of more precise, even measurements of time and helped the 24-hour day with equal-length hours gain greater popularity.
The more mechanical clocks spread and reached into the cultures of the West, the deeper they cut. It spread further with European colonization and global trading, becoming universal in its standard usage; people now needed a better way to orient their daily routines and international transactions.
Why 24-Hours and Not Another Number?
The selection of 24 hours could be linked to the convenience of division associated with the Egyptians' use of the duodecimal system. The base-12 provides greater flexibility concerning the division of time, hence it was a natural double for both day and night representation. Also, the rotation period of the Earth, being close to about 24 hours (in reality around 23.93 hours), allows a reasonably good approximation of a complete cycle of light and darkness during the day.
More importantly, the base-60 system of the Sumerians has significant impacts on how we count minutes and seconds, too, and can be pretty handy for dividing time into smaller, more manageable units. The layering of convenience, observation of natural cycles, and mathematical convenience helped solidify the division of the day into 24 hours.

A Meld of Nature and Human Ingenuity

A 24-hour day system is not something that is arbitrarily divided in time but evolved from cycles and observations of the heavens as well as cultural developments. It ranges from the base-60 calculations by the Sumerians to dividing day and night with the Greeks and Romans, perfecting, and then generalizing it into what we know today as timekeeping. The 24-hour system persisted for the simple reason that it worked—it found an equilibrium between practicality and the rhythms of the natural world.
We don't even notice this anymore, but our very perception of time was created a long, long time ago out of an ancient innovation. There went mechanical clocks and then electronic devices to end their reign supreme over our organizational activities in the 24-hour day.

Conclusion

The 24-hour day has its history going back thousands of years deep in human history and was founded upon the planet's natural cycles. Development and upscaling over several hundred years came from ancient civilizations like the Egyptians, Sumerians, Greeks, and Romans, who through advances in science and technology, fine-tuned this 24-hour day into what it has been for centuries.
Although perhaps a little dated, this, along with the waters of clock-time and pebbles in bottles, will remain the constantly evolving manner of how we reckon time. However, for the foreseeable future at least, the 24-hour day will remain an indispensable part of our daily lives, guiding us through the ups and downs of every given day.