The contemporary method of measuring time – comprising 24 hours in a day, 60 minutes in an hour, and 60 seconds in a minute – is a heritage of 5,000-year-old decisions that have outlived the civilisations that conceived them.
This “ingrained” system has persisted despite radical historical attempts to overhaul it, most notably during the French Revolution.
France’s ill-fated decimal experiment
In October 1793, the newly established French Republic attempted to rationalise time by introducing a decimal system. Under this mandate, a day consisted of 10 hours, with each hour containing 100 minutes décimales and each minute consisting of 100 secondes décimales. This was part of a wider revolutionary calendar that included a 10-day week aimed at “de-Christianising” the year.
However, the experiment caused significant “headaches,” according to Finn Burridge, a science communicator at Royal Museums Greenwich. Redesigning clocks proved difficult, and the system isolated France from its neighbours. Claude-Antoine Prieur, a member of the French National Convention, argued in 1795 that the system offered no marked advantage. Ultimately, decimal time lasted only 17 months.
Mesopotamian mathematics and sexagesimal system
The origins of our current timekeeping lie with the Sumerians of Mesopotamia (modern-day Iraq), who thrived from approximately 5300 to 1940 BC.
They developed a mathematical system based on the concept of 60, known as a sexagesimal system. Martin Willis Monroe, an expert in cuneiform cultures at the University of New Brunswick, noted that the development of written numbers was driven by the need for complex farming records.
One theory suggests the base-60 system originated from counting the 12 joints on the fingers of one hand and using the five fingers of the second hand to track each count of 12. Erica Meszaros, a historian of exact sciences from Brown University, highlighted that 60 is highly practical because it can be divided by multiple factors (1, 2, 3, 4, 5, 6, 10, 12, 15, 20, and 30) without requiring fractions.
While the Sumerians provided the numerical base, the ancient Egyptians were the first known to divide the day into hours, appearing in religious texts around 2500 BC. Rita Gautschy, an archaeoastronomer at the University of Basel, stated that early Egyptian “star clocks” found in coffins from 2100 to 1800 BC referred to 12 hours of the night. By the Roman period, hours became the standard for daily life.
The Babylonians (2000–540 BC) later adopted the Sumerian sexagesimal system and refined these divisions. For astronomical calculations, they divided the day into 12 beru (double-hours), which were further broken down into 30 ush (four modern minutes) and 60 ninda (four modern seconds).
These subdivisions were adopted by the Greeks in the Hellenistic world after 330 BC to maintain consistency with existing Babylonian astronomical data.
Technological evolution and atomic age
It was only within the last few hundred years that timekeeping devices became accurate enough for minutes and seconds to be used in daily life. The timeline of accuracy progressed from 12th-century mechanical clocks to 18th-century watches that would not lose minutes for weeks.
In the 20th century, the development of atomic clocks allowed scientists to redefine the second based on the microwave radiation of caesium-133 atoms.
Today, this global network of atomic clocks supports the internet, GPS, and medical imaging. Despite these technological leaps, the ancient 60-unit structure remains, as changing such a deeply embedded system is considered “too much to handle” for modern society.
