Why 1 hour lasts exactly 60 minutes, and a minute exactly 60 seconds?

Pocket Watch

Pocket Watch

Frequently asked question: Why 1 hour lasts exactly 60 minutes, and a minute exactly 60 seconds?

Who is the one who put the regulation to separate the day of 24 hours, while hours equals to 60 minutes and one minute equal to  60 seconds? Why the number 60 ? Since when to we practice this, is it always been the same or time evolved itself through time.



Egyptian Sun Clock

Egyptian Sun Clock

Many historians believe that the Egyptians were the first civilization that has divided the day into smaller parts.  The first solar clocks were actually simply placed stakes to track the time, and in about 1500. BC Egyptians has already developed advanced solar clocks. In fact, rod-shaped “T” were placed on the ground, and the period between sunrise and sunset was divided into 12 parts,  reflecting Ancient Egyptian duodecimal system. The sun clocks of the “newer” generation slowly started to follow that first Egyptian principal and now we not it as a clock.

However, the hours during the day were ( more or less) the same, but they were not equal through out the year. Let’s say summer hours lasted longer than the ones in winter. In a world without artificial lighting, day and night were contradictory meaning they were not considered as part of one day, as a whole. At night which there is no sunlight and no shadows, it is harder to divide in stages, monitor and come to a decisive result.

But by the time when the Egyptian astronomers saw the use of the sun clocks and started using them, they were supervising 36 stars who divided the firmament in equal parts.

Water Clock (clepsydra)

Water Clock (clepsydra)

The night followed by the appearing of 18 of those stars, and 3 of them were aligned in a particular way that only can be seen at dusk. Then a complete darkness marked the emergence of 12 stars throughout the night, thus splitting the night in 12 parts. At the time of the New Kingdom , this system is simplified so that temporal orientation used only 24 stars, of which observed 12 marked the night. By then in use was already and the water clock (clepsydra), which represent perhaps the most accurate way of measuring time in the old world.

And when day and night were divided into 12 parts, only then was born the concept of 1 day consisting of 24 hours.

However, clearly fixed duration of every hour that make up the day, will not live up until the Hellenistic era, where the Greek astronomers began to use such systems for their own theoretical questions and assumptions. Hipparchus of Rhodes and other astronomers applied astronomical techniques which originally were developed by Babylonians.

Their calculations were based on Sexagesimal System ( based on the number 60) , inherited by the Sumerian, it is still not clear till this day why the choice of the number 60,  but it is suspected barbecue it was suitable for the following: – 60 is the smallest number divisible by the numbers 2, 3 , 4 , 5 , 6, 10, 12 , 15, 20 and 30.


Sexagesimal (base 60)

Greek astronomer Eratosthenes used the Sexagesimal System trying to divide the circle of 60 parts while working on early system about geographical latitude. A century late, Hipparchus wrote down parallel lines that concerns latitude and matches the geometry of the Earth.

A century later, Hipparchus prescribed parallel lines that are concerned latitude , which it matched the geometry of Earth.

His work was explained and expanded by Claudius Ptolemy, stating that 360 degrees latitude and longitude were divided into smaller the segments . Each degree divided into 60 parts, and those to further 60 even smaller. The first part – partes minutiae primae – or first minute, became known simply as a MINUTE. A segment in its interior – partes minutiae secundae – became known as the SECOND.

However, hour of 60 minutes did not immediately appear on the watches. They were different types such as Clocks showing the hours divided into halves , thirds , quarters and sometimes even twelfths , but never 60 parts. In ancient times, long before the appearance of the mechanical clock , the general public opinion was that its not practical to consider the minutes.

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