A mathematical choice made by ancient civilisations thousands of years ago still determines how modern societies measure time.
When the French Revolution attempted to redesign time in 1793, the reformers believed the system could be simplified. They introduced a decimal day divided into 10 hours, each hour into 100 minutes and each minute into 100 seconds. New clocks were manufactured and official activities began using the revolutionary calendar.
The experiment quickly failed. Converting clocks proved difficult, the system isolated France from neighbouring countries and the population resisted the idea of having a rest day only every tenth day. Decimal time survived barely more than a year.
The episode revealed how deeply the traditional system of 24 hours, 60 minutes and 60 seconds is embedded in society, a structure whose origins stretch back more than five millennia.
The Sumerian Origin Of Base-60 Mathematics
The roots of modern time measurement lie in ancient Mesopotamia, in the civilisation of the Sumerians, who lived roughly between 5300BC and 1940BC in what is now Iraq. The Sumerians were among the first societies to build cities and are credited with major innovations including irrigation systems, the plough and the earliest known writing system.
Their writing, known as cuneiform, was often impressed onto small clay tablets used to record agricultural production, trade and taxes. These tablets also reveal one of the earliest known mathematical systems.
Unlike the modern decimal system based on ten, the Sumerians developed a system based on sixty, known as the sexagesimal system. In this system, numbers increase up to 59 before moving to the next place value.
Scholars are still uncertain why the number sixty was chosen. One theory suggests it may relate to counting using finger joints. Each finger, excluding the thumb, has three joints. Counting the joints on four fingers gives twelve. Using the other hand to count the cycles of twelve leads to sixty.
Regardless of its exact origin, the system proved extremely practical. Sixty can be divided evenly by many numbers, including two, three, four, five, six, ten, twelve, fifteen, twenty and thirty. This made calculations easier in fields such as accounting, land measurement and taxation.
From Mathematics To Astronomy And Time
The Sumerian mathematical tradition was inherited by the Babylonians, who flourished in Mesopotamia between roughly 2000BC and 540BC. They adopted both the cuneiform script and the base-60 numerical system.
By around 1000BC, the Babylonians had developed astronomical calculations that required precise numerical divisions. Their calendar followed the solar cycle of slightly more than 360 days, a number that worked conveniently within a base-60 system.
Babylonian astronomers divided the day into large units and then into smaller fractions for astronomical calculations. A double hour known as a beru could be divided into 30 smaller units, and these were further divided into sixty parts.
These divisions were not originally designed for daily timekeeping. Instead, they were mathematical tools used to track the movement of celestial bodies and to calculate planetary positions.
Nevertheless, the numerical framework created by Babylonian astronomy would later influence how time itself was measured.
The Egyptian Division Of The Day
While Mesopotamian mathematicians refined the numerical system, the ancient Egyptians were developing the concept of dividing the day into hours.
Religious texts from around 2500BC refer to divisions of the night into twelve parts. Archaeologists have discovered so-called diagonal star clocks painted on the lids of Egyptian coffins dating from around 2100BC to 1800BC. These charts tracked the rising of specific stars and marked the passage of twelve nighttime hours.
Later, the Egyptians also divided daylight into twelve hours, creating a 24-hour day. The exact reason for choosing twelve remains uncertain, though several theories exist.
Some historians suggest it relates to the twelve constellations associated with the zodiac, while others point again to the finger-joint counting system that allows counting to twelve using one hand. Another possibility is that the number related to astronomical observations of stars appearing in the night sky.
By around 1500BC, Egyptians were using sundials and water clocks, among the earliest known devices for measuring time. These instruments were often used in religious contexts and temple rituals rather than everyday scheduling.
In daily life, people generally measured time in broader units such as morning or afternoon work shifts.
How Minutes And Seconds Emerged
The Greek scholars of the Hellenistic world inherited both Egyptian time divisions and Babylonian mathematical traditions. Centres of learning such as Alexandria became hubs where knowledge from across the Mediterranean and Near East was combined.
Greek astronomers adopted the Babylonian base-60 system because it allowed them to integrate new astronomical observations into existing calculations. Over time, they applied the same numerical subdivisions to the measurement of time itself.
This is how the hour eventually came to be divided into sixty minutes and each minute into sixty seconds.
For centuries, however, these smaller units were largely theoretical. Mechanical clocks did not yet exist and early timekeeping devices were not accurate enough to measure minutes or seconds reliably.
The Evolution Of Accurate Timekeeping
The development of mechanical clocks in Europe during the 12th century allowed time to be measured to roughly the nearest hour.
In the 16th century, pendulum clocks improved accuracy but could still drift by ten to fifteen minutes per day. It was only in the 18th century that highly precise watches were developed, making minutes and seconds practical units for everyday use.
Further breakthroughs followed in the 20th century. Quartz clocks, introduced in the 1920s, could keep time with extraordinary precision, losing only a second every few years. Atomic clocks developed in the 1950s pushed accuracy even further by measuring the oscillations of atoms, allowing time to be defined with extraordinary stability.
Today, global networks of atomic clocks synchronise the time used for technologies such as GPS navigation, telecommunications and internet networks.
Why The System Still Exists Today
The system of hours, minutes and seconds has survived thousands of years largely because it works. The base-60 structure allows convenient mathematical divisions and has become deeply embedded in science, engineering and everyday life.
Attempts to replace it, such as the French revolutionary decimal time experiment, have failed because the cost of changing global systems far outweighs the benefits.
As a result, a mathematical decision made by ancient civilisations more than 5,000 years ago continues to shape how modern societies measure and organise time.
Source: BBC news