Why An Hour Has 60 Minutes (101.html)
by David KC Cole

Table of Contents
External References (Sources)

Introduction This article explains how the various time intervals probably evolved. Some ancient explanations are only plausible. But the more recent developments presented are very factual and name the individuals involved. Sources are included at the bottom of the article

(Click on this photo to enlarge it.)
thumb: ARoman Water Wheel
Roman Water Wheel

Why an hour has 60 minutes

Hours, Months, Years, Minutes


The very first people on the earth knew that the sun rises each morning and that it sets each evening. We say that the sun rises and sets every day. This length of time called a "day" was probably the first notion of a period of time. Eventually, after people learned how to count, they were able to count the number of days. They could say that it has been 10 or 15 days since a certain notable event happened. But other ideas of time took much longer to discover.

A long, long time ago, shepherds were very bored, night after night, while they watched their sheep. Many of them started watching the stars all night long. Of course, they noticed that almost all of the stars never changed positions, although the whole sky rotated overhead. These fixed stars remained stationary in the sky relative to each other. The shephards imagined pictures in the night sky, formed by imaginary lines linking some of the stars. (Through the ages, astronomers have assigned names to the main shapes in these pictures. A "constellation" is the scientific word for such a shape.) Most of the shapes of these imagined pictures were familiar animal shapes. They imagined such things as lions, goats, fish, scorpions and even people. They noticed that as the moon travelled across the sky, it passed between some of these stars, passing through each shape. When this happened, they said the moon visited one of these shapes. It took the moon less than 3 nights to move through each shape. About every 28 days, the moon visited the same 12 shapes . . . . . over and over again . . . . month after month after month. The moon only visits these same 12 special shapes, it never visits any of the other shapes in the night-time sky. The shepherds gave each of these 12 shapes a different name. The first shape was a goat named Capricorn. Then they imagined a woman carrying water in two pails suspended on each end of a yoke that she carried across her shoulders. Her name was Aquarius. These 12 pictures, or signs, were called the Zodiac. The Greek word "Zodiac" appropriately means circle of animals. We still use the word, Zodiac, when we speak of these 12 signs. The 12 signs of the Zodiac visited by the moon every month were named: Capricorn (goat), Aquarius (water-bearer), Pisces (fish), Aries (ram), Taurus (bull), Gemini (twins), Cancer (crab), Leo (lion), Virgo (maiden), Libra (scales), Scorpio (scorpion) and Sagittarius (archer). Because the moon returned to the same sign after about 28 days, the shepherds said that each period of about 28 days was a month.

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thumb: Signs Of The Zodiac
Signs Of The Zodiac


They also noticed that once about every 28 days the moon was a fully lit circle. Then a sliver of the moon became darker each day, and after 7 days, the lit-up part of the moon was only the left half of a circle. After another 7 days, the moon was completely dark. After another 7 days, the other half of the moon was lit up. Finally after another 7 days the moon was a fully lit circle again. They called a fully lit moon, a "full moon". This name is used even today. Today, we say that the moon has four phases, each phase being approximately 7 days. I believe that this is the reason that we say that 7 days is a week. (But no-one knows this for sure.)

Week-Day Names

The ancient Greeks had also noticed that some "stars" were not "fixed stars". These moving stars were thought to be gods that moved in the sky between the signs of the Zodiac. (Ancient storytellers made up stories about what happened to these gods as they visited the constellations. Since the invention of telescopes, we now know that these moving stars are planets that move in near-circles around our sun. Before telescopes were invented, with their naked eyes, people could only see the following moving stars: Mercury, Venus, Mars, Jupiter and Saturn. They also knew that the Sun and the Moon moved between the stars in the sky. This made 7 "moving heavenly bodies" that visited the pictures in the sky. They named each day of the week after each of these 7 "moving heavenly bodies". In English, these names are respectively: Wednesday, Friday, Tuesday, Thursday, Saturday, Sunday and Monday. In French, these names are respectively: mercredi, vendredi, mardi, jeudi, samedi, dimanche and lundi. Careful examination of these 14 weekday names permits us to identify to which "moving heavenly body" each weekday was assigned.

Names of Months

These early moon-watchers noticed another strange thing about the moon. . . . Each month, the full moon would visit a different sign of the Zodiac. So every 28 days they started calling this new period of 28 days a different name. This new different name was the name of the sign that the full moon was visiting. So way back then, the names of the months were the names of the signs of the Zodiac. Instead of saying the 3rd day of March, they said the 3rd day of Capricorn. (But don't jump to the conclusion that March means Capricorn, because it doesn't.)

The names of the months originally were simple numbers. The mundane winter months were last on the list. The center column shows the month names in English. The rightmost column explains why the month was given a name instead of a number.

11Januarygod: Janus
12FebruaryFebrua (purification)
1Marchplanet: Mars -Year begins
2Aprilaperir (to open)
3Maygoddess: Maia
4Junegoddess: Juno
5Julyemperor: Julius Caesar
6Augustemperor: Augustus Caesar


Everyone knew that the four seasons repeated over and over again, and this period of almost exactly 365 days was called a year. People measured long periods of time in years. Most people knew how many years they had lived. They said that this was their age. Some people, those who seriously studied the sky, knew that the Sun rose in a different position of the Zodiac each day. Between 10,00 and 4,000 years ago, the ancient people in Britain knew this and created Stonehenge to celebrate the spring and/or autumn solstices. The spring solstice is the day of the year when the Sun rises in the point on the horizon that is the most northern at dawn. On this day, the Sun was always visiting the same sign of the Zodiac. In 2013, the Sun rose in the constellation known as Pisces, as can be seen in the image below:

(Click on this photo to enlarge it.)
thumb: Vernal Equinox, March 20, 2013
Vernal Equinox, March 20, 2013

If proven true, Source 7, an astrology web-site, says that,
"a current controversial dating of the stones at Karahundj [in present day Armenia] predate England's Stonehenge, they predate the Babylonian's claim to being the first astronomers, and they confirm what some people already suspect: that Armenia is the birthplace of the zodiac, and perhaps the beginning of navigation and the concept of time.......7000 BC"

However,Source 8 says that most of the information in Source 7 is unproven and ends with the statement:
. . . . . . As a consequence, González-Garcia concluded that the archaeoastronomical claims for the site are untenable, although further investigations to determine the astronomical potential of Carahunge and similar sites are merited.

How many days in each month?

Each group of 12 months (12 x 28 days = 336 days) was also thought to be a year, as if the moon were exactly synchronized with the seasons, but it wasn't. They finally discovered that there were 29 (365-336) extra days to be dealt with. Eventually, it was agreed to assign each month 30 days instead of 28 days. This left only 5 extra days, so the months that we call January, March, May, July, August, October and December were given an extra day. But because that made 7 extra-long months of 31 days, one of the months needed to lose 2 days. . . . That is why February has only 28 days. I have greatly simplified this explanation . . . . actually it was extremely difficult for the scientists and heads of countries to understand this completely. It was even harder for them to all agree which months should be longer etc. It took thousands of years for the months and years to be correctly handled, counted or managed by society in general. Even today, some societies haven't adopted this new calendar.


Everyone could see that all 12 of the signs of the Zodiac appeared across the sky throughout the night, although only half of them were visible at any one time. People knew that the period of the night-time darkness was approximately the same as the period of daylight each day. (For people living near the equator, this was true all year long.) Everyone can see the sun travel across the whole sky each day. Imagine if you could see the 12 signs of the Zodiac moving across the sky each day just like they do at night. The sun might be passing through each of the 12 signs each day. (During an eclipse of the sun, the stars can be seen in the sky behind the ecliped sun.) So we might conclude that the sun also passes through each of the 12 signs each day. Between eclipses (which is most of the time) you cannot see the signs of the Zodiac during the day, but they are certainly there. So, people probably decided to divide the daytime into 12 time periods, one for each sign that the sun might be "passing" through. Each night was, of course, divided into the same 12 time periods. Each of these time periods was eventually called an hour. These 2 Zodiacs that crossed the sky each day is probably why there are 24 hours in each day. Scientists or astronomers will certainly argue with this explanation, but until another better explanation comes along, I will stick with this one.


The notion of short periods of time is much more difficult to understand. Humans like other similar animals have beating hearts. Counting your heart-beats is called measuring your pulse. Anyone can sense their pulse by feeling an artery on the wrist or neck. An alert person has a good idea of the length of time (or time period) between two successive heartbeats. Today, we know that a heartbeat is about 1 second long. But why did people decide to call it a second? I have never seen or heard an explanation, but I believe the following theory:

First, we must think of a few special people (living long ago) who wanted to know what time it was. Perhaps they wanted to know when it was time for the next meal each day or if it was time to say their prayers. People needed clocks, but clocks had not yet been invented.


People who work and live out-of-dors notice that the shadow cast by a tree or pole moves all day long. One day, someone traced the end of the shadow on the ground and noticed that the shadow made a curve on the ground. This curve was the first type of clock ever made. On clear nights, the moon shone down and its shadow followed exactly the same curve. Then they marked on the curve the 12 signs of the Zodiac that they saw every night. (The moon didn't visit all of these signs during the night but it was visible that all 12 signs could be seen each night. This is how the first hours originated. The moon didn't visit every sign each night as it traced half a circle through the sky. But the curve of the 12 signs of the Zodiac matched the half-circle that the moon (and sun's) shadow traced on the ground during the day-time and night-time part of each day. Each day the sun and then the moon passed through each of the 12 signs of the Zodiac. Tall trees or small poles produced exactly the same shadow curve. A SunDial simply shows the shadow traced by the sun during the 12 hours of daylight.

Improved Sun-Dials

As years went by, people found that it was more convenient if the time intervals between each of the 12 Zodiac signs on the SunDial were identical. There were other means of measuring time, such as the regular footsteps when an army marched. So people could tell when the time intervals on the "improved" SunDial were the same. These new markings on the SunDial didn't exactly match the widths of the signs of the Zodiac in the sky. But that didn't matter, this "improved" SunDial was much more useful than the original SunDial. The new markings used by the Arabs were simply labelled 1, 2, 3 . . . . .12. The Romans also used this type of improved SunDial but with Roman numerals. For years and years, and even today, some clocks use Roman Numerals for the markings on their faces. This is why we see I, II, III, IV, V, VI . . . . XII on many clocks. Big Ben, in London, England, the most famous clock in the world, has Roman Numerals on its face. Most SunDials also show Roman Numerals on their faces. Builders of SunDials have found that the hours appear perfectly if the pole is slanted at a special angle depending upon where the SunDial is used. Unfortunately a SunDial that works well at one location doesn't always work well at another location. Another disadvantage was that SunDials didn't work indoors, nor at night nor when it was cloudy.

Hourglass Clocks

Another type of clock eventually was invented that worked better than a SunDial. In this type of clock, grains of sand drop through a narrow opening from one glass container into a second glass container. Any exact period of time can be measured by putting the correct amount of sand in the top container. Once the correct amount of sand is placed in a glass container, both the top and bottom containers can be sealed. These first "glass" clocks measured exactly one hour, so they were called "Hour-Glass" clocks. After each hour, the hourglass must be turned over to begin timing the next hour. By doing this, it was possible to know the exact time or hour, 24 times per day. These Hour-Glass clocks worked well at most locations. Furthermore they worked at night and on cloudy days. But they were more expensive to build and they needed to be operated by someone, all day and night. Slaves were probably assigned to this job. (It is not known who first invented the Hour-Glass.)


Many kitchens have a smaller type of "hourglass" called an "Egg-Timer". Today's egg-timers measure 3 minutes, which is the approximate time that it takes to soft-boil a chicken's egg in boiling water . . . .


The Romans invented a different type of clock, known as a water-clock. In these clocks, water dripped into a cylinder. The rising water level in the cylinder slowly raised a float. The float raised a notched stick that turned a gear. The gear turned a needle. A picture of a water-clock appears at the beginning of this article. Some sophisticated models apparently had a clock-face (like a SunDial or a modern clock) with numbers 1 to 12 written around the face of the clock where the single needle indicated the hour. In those days, long ago, minutes had not yet been invented. Perhaps, one of those Romans made a water clock using drops of water that dripped at a rate of one drip per second, to match a human heartbeat. It is not hard to imagine that some clock-maker added another hand to the face of the clock. This additional hand (or needle) was probably designed to make one revolution each hour. This additional hand might have existed before minutes were even considered. This additional hand would have easily shown "quarter after" or "half past" the hour. Perhaps this terminology began soon after this additional hand was added. Most people sleep at night, so this type of clock only needed to show the 12 hours during each day. People who lived far away from the equator found that summer days were longer than 12 hours, but this type of clock could be easily modified to display more hours.


Probably, there was a "Eureka" moment when a [Sumerian?] mathematician noticed that there were approximately 3600 heartbeats in an hour. He would have remarked that 3600 was 60 squared. It would not have been a "big leap" for him to divide the clock-face into 60 intervals by separating each "hour" of the clock face into 5 divisions. These smaller intervals might have been called "minute" (ie diminutive) intervals. Of course, 5 divisions times the 12 "hour divisions" makes a total of 60 "minute" divisions per hour.

Phil Molyneux, in the Guardian (Source 6) says that there are 60 minutes in an hour because the Sumerians used 60 as their number base. But I believe that the Sumerians used 60 as their number base because there are about 3600 heartbeats in an hour. (What came first: the chicken or the egg?) In return, I ask Phil Molyneux: Why did the Sumerians use 60 as their number base?


It was then very easy for this (or a subsequent) clock-maker to add another hand to the mechanism. This "third" hand could make use of exactly the same divisions on the clock as the minute divisions. In this way, every heartbeat could be easily counted as this last hand moved from one minute division to the next. All that was needed was to give a name to this last interval, the smallest interval of time for this new clock. The "minute" was the name of the FIRST small interval of time. Perhaps the next smaller interval of time was simply called the SECOND small interval. But one thing is certain . . . this second interval would be approximately equal to the length of a heartbeat. Around 1000 years ago, an Arab named al-Biruni was the first person who wrote about this time interval. In Source 3 below, we see that he called it a "second" in Arabic.

It was decided, in some way similar to this, that there should be 60 minutes in each hour and 60 seconds in each minute. So, once minutes and seconds had been defined, everyone could forget about a second being approximately the length of a heartbeat. (I feel that we should have called a second a "beat", because we call 12 inches on a ruler a "foot".) Wikipedia states that today, around 2015 CE, a normal human heartbeat happen once every 0.8 seconds. This corresponds to a pulse rate of 75 beats per minute. Measure it yourself.

In Source 4, Wikipedia states:
The second became accurately measurable with the development of pendulum clocks keeping mean time (as opposed to the apparent time displayed by sundials). In 1644, Marin Mersenne calculated that a pendulum with a length of 39.1 inches (0.994 m) would have a period, at one standard gravity, of precisely two seconds, one second for a swing forward and one second for the return swing, enabling such a pendulum to tick in precise seconds.

In 1670, London clockmaker William Clement added this "seconds" pendulum to the original pendulum clock of Christiaan Huygens.[Source 5] From 1670 to 1680, Clement made many improvements to his clock and introduced the longcase or grandfather clock to the public. This clock used an anchor escapement mechanism with a seconds pendulum to display seconds in a small subdial. This mechanism required less power, caused less friction and was accurate enough to measure seconds reliably as one-sixtieth of a minute than the older verge escapement. Within a few years, most British precision clockmakers were producing longcase clocks and other clockmakers soon followed. Thus the second could now be reliably measured.

Scientific Definition of a Second

Source 3 states that:
In the year 1000 CE, the Persian Muslim scholar al-Biruni first used the term second in Arabic and defined it as 1⁄86,400 (that is, 1/(24 × 60 × 60) of a mean solar day.

In 1960, this definition was made more precise by adding the words "of the tropical year for 1900 January 0 at 12 hours ephemeris time." Seven years later, the second was redefined very precisely in terms of the radiation of the caesium-133 atom.

Numbering the Years

In ancient literature, the years were numbered by stating something like "In the 13th year of the reign of King Alfred IV . . .". This was one way of specifying an exact year. Historians have worked hard to know exactly which year is meant in each case. But the best way to number years has been to choose a certain special event (or epoch) and call it year 0. Then a specific year can be identified by specifying the number of years before or since that date. Most countries have agreed to use the birth of Jesus Christ as being the certain special event. Two years before that specific event is specified as 2 BC. Four hundred years after that event is 400 CE (formerly 400 AD). Today, we normally omit the CE or AD designation. Non-Christian countries such as China and Israel use a different special event.

Some computer operating systems do it differently. Unix (and subsequently Linux) use Jan 1, 1970 as the 0 time (ie the Unix epoch). Then a Unix timestamp (UTC) specifies the number of seconds since or before the beginning of that year. Negative values of UTC refer to time before the Unix Epoch. The current UTC in November 2015 is 1447658244. Nowadays, most computer operating systems understand the Gregorian calendar, and use the internet to synchronise themselves with a central world clock. Computers equipped with GPS can easily know in which Time-Zone they are located.

Julian Calendar

The Julian Calendar is defined as:
A calendar introduced by the authority of Julius Caesar in 46 BC, in which the year consisted of 365 days, every fourth year having 366 days. It was superseded by the Gregorian calendar though it is still used by some Orthodox Churches. Dates in the Julian calendar are sometimes designated “Old Style.”

Gregorian Calendar

The Gregorian Calendar is defined as:
The Gregorian calendar reformed the Julian calendar because the Julian calendar introduced an error of 1 day every 128 years. The introduction of the Gregorian calendar allowed for the realignment with astronomical events like equinoxes and solstices, however a number of days had to be dropped when the change was made.

The switch from Julian to Gregorian
The Gregorian calendar was first adopted in Italy, Poland, Portugal and Spain in 1582. The Gregorian reform consisted of the following changes:

i 10 days were dropped in October 1582.
ii New rules were set to determine the date of Easter.
iii The rule for calculating Leap Years was changed to include that a year is a Leap Year if:
- The year is evenly divisible by 4;
- If the year can be evenly divided by 100, it is NOT a leap year, unless;
- The year is also evenly divisible by 400. Then it is a leap year.
Is there a perfect calendar?
Was February 30 ever a real date?
For example, the years 1900, 2100, and 2200 are not Leap Years. However, the years 1600, 2000, and 2400 are Leap Years.

The Julian calendar is currently (between the years 1901 and 2099) 13 days behind the Gregorian calendar because too many Leap Years were added. The Gregorian calendar [will be] off by about 1 day every 3236 years.

Switching to the Gregorian Calendar

The Gregorian calendar would not be adopted until much later in Great Britain and America. It wasn’t until September 1752 that 11 days were dropped to switch to the Gregorian calendar.


This article has described a plausible way for having defined the lengths of the following time periods: Days, Months, Years, "Half Moons", Weeks, Hours, Minutes and Seconds. Also a probable evolution of the names of the months and weekdays has been included.

The end.

External References (Sources)

(where possible, www is a weblink to the original source; the second weblink leads to a copy of the information that I have preserved.)

The webmaster makes copies of webpages, as well as a weblink to the original source because so much information gets lost on the web after one or more years because a website dies or because subpages are moved and the original weblink no longer exists even if web indices such as Google still list them.

Source 1: www Cardiac Cycle Wikipedia 2015
Source 2: www Gregorian Calendar 2015
Source 3: Book: al-Biruni (1879). The chronology of ancient nations: an English version of the Arabic text of the Athâr-ul-Bâkiya of Albîrûnî, or "Vestiges of the Past". Sachau C Edward. pp. 147–149. 1879
Source 4: www Wikipedia:second 2015
Source 5: Book: "The Long Case Clock: The Science and Engineering that Goes Into a Grandfather Clock". Illumin 1: 1. by Jessica Chappell (Oct 1, 2001).
Source 6: www Why are there 60 minutes in an hour? Phil Molyneux, before 2015
Source 7: www Karahundj is older than Stonehenge An astrology site
Source 8: www Carahunge was not an astronomy site Wikipedia: comment by Gonazlez-Garcia in 2014

WebMaster: Ye Old King Cole

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Last Updated: 2015 K Nov 19

Date Written: 2015 J Nov 16