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Days of the Week (Calendar)

Days of the Week Calendar

Calendar, Names Of Days

One of Man’s earliest and greatest inventions was that of the Calendar and correspondingly, time measurement standards such as Months, Weeks and Days
The Calendar is an indispensable part of everyday life. Calendars allow man to track passing time and to prepare for the future. Calendars help man know when to plant, when to prepare for festivals and other important events, when to prepare for harsh weather, when to celebrate his religion, his own birthday and much more.

The Calendar is a deceptively simple tool. It is a means of counting the days and organizing them into agreed upon standard units such as weeks, months and years. These units generally derive from recurrent astronomical cycles, which are among the most constant and most conspicuous changes in nature. 

Day, Week, Month

The day is derived from the earth’s 24 hour rotation on its axis.  The month and likely the week are based on the phases of the moon. The year measurement is based on the tilted earth’s revolution around the sun. Observing, measuring and recording these cycles may appear simple but organizing these units into practical time reckoning systems has challenged man’s scientific resources for thousands of years.  Even today, we do not and cannot have a completely accurate Calendar. We simply have a Calendar that is good enough to serve our needs.

The Calendar and Religion

Religion has played a major part in the development of the Calendar. Throughout history, man’s tendency to worship heavenly bodies as well as observe and record them has given Calendar development a religious significance. Centuries upon centuries religious priesthoods, dogmas and recordings have been involved with time reckoning; establishing Calendars, reshaping old Calendars and promoting or blocking the adoption of new Calendars.

The Sumerians

The earliest known development and use of a Calendar happened about 5,000 years ago, in the Middle East along the banks of the Tigris and Euphrates Rivers, in an area which is now Iraq. The Sumerians were a very advanced people who developed the first literate, sustainable and town based urban culture. Sumerian priests who were mostly responsible for keeping records of their everyday activities were also their society’s specialists of time management.

For the Sumerians to survive and prosper; everyday activities such as planting, harvesting, building, weaving and more, needed to be organized and managed. Sumerian priests and other leaders organized these activities and kept records on tablets of clay. These records were valuable in not only helping to manage daily activities but in helping them prepare for future activities such as when the wheat and barley fields will be ready to harvest.

The Sumerian Calendar was thus developed and used to insure orderly and predictable management of their society’s resources. 

It is believed that the Sumerian priests based their original Calendar on the changes of the moon. They divided their year into twelve lunar units, or months, of 30 days each. However, this measurement presents a problem. The year is measured based on the revolution of the earth around the sun, which comes to about 365 ¼ days. The month is measured by the phases of the moon, the full cycle of the moon takes about 29 ½ days. Therefore, the year is not composed of 12 equal months but about 12 1/3 months. Without corrections, the Sumerian Calendar would have quickly become out of sync with the moon and sun. The Sumerians must have made corrections but how this was done is unknown. The Babylonians and Egyptians later improved upon the accuracy of the Sumerian Calendar. Further improvements were made by Roman and Middle Age European religious leaders and scientists. The important fact is that an advanced, very accurate time measurement system known as a Calendar was developed and used by ancient Sumerians to further advance their already impressive civilization and set the beginning of Man’s ongoing management of time. 


The further measurement of time that divided the Calendar developed into Months. The Western and generally accepted names of our months evolved from Roman gods Janus and Mars and the goddesses Maia and Juno. Additionally, Roman Latin names for numbers, events and people give us names of our months. July is named from the time Julius Caesar was born, December is derived from Latin “decem” or ten; April is derived from Latin “aperire”, meaning “to open”, when flower buds open. 

7 Day Week

The concept of the Seven Day Week is believed to have its origin from the ancient Jews. Early measurements of the week likely were based on time intervals between farming activities, religious ceremonies, market days and more. The time measurement of weeks based on early Man’s activities ranged from four to ten days. The Jewish Calendar divided the week into seven units or days. It is believed that the adoption of the number seven for measuring time was based on supposed mystical and religious properties. Seven was considered lucky in ancient times (as it is even today). Moreover, seven days is approximately one quarter of a lunar month. Observing the time in which the moon went through its different full moon, half moon phases may have convinced the Jews to adopt this measurement.

Over time, improvements to the concept and use of the Calendar, the month, week and day were developed and adjusted to improve accuracy. Today we still use the time measurements of the Calendar to help us in almost every aspect of our lives.

Origin of The Names of The Months

January – from the Roman god Janus, god of beginnings and endings, the month Januarius

February – from Roman god Februus and/or februa, signifying purification festivals celebrated by Romans at this time of the year

March – from the Roman god of war, Mars

April – from Latin, aperire, “to open”, likely named to denote the time of year when flower and plant buds open

May – believed to have come from Maiesta, the Roman goddess of reverence and honor

June – from Juno, the Roman goddess who is the protector of the state and mother of Mars and Vulcan and possibly from Latin,  juniores, young men or juniors, who were celebrated at this time of the year

July – named in honor of the great Roman emperor, Julius Caesar, who was born at this time of the year

August – named in honor of the Roman emperor, Augustus, as fortunate events occurred for Augustus during this time of the year

September – from Latin, septem, “seven”

October – from Latin, octo, “eight”

November – from Latin, novem, “nine”

December – from Latin, decem, “ten”

Origin of the Names of Days

Sunday – from Latin dies solis, Sun’s Day
Monday – from Latin dies lunae, Moon’s Day
Tuesday – from Tiw, Teutonic/Viking god of Law
Wednesday – from Woden, Teutonic/Viking god of gods
Thursday – from Thor, Teutonic/Viking god of war
Friday – from Fria, Teutonic/Viking god of love
Saturday – from Saturn, Roman god of agriculture


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