Why Are There Seven Days in a Week?

You probably dread Monday mornings and wonder why you have to wait for another five days until the weekend. We’ve all grow up knowing the seven days of the week, but have you ever taken time to think how these days came about?

There are so many questions a curious mind would want to know:
• Where did the names come from?
• Who invented the days of the week?
• Why seven days in a week and not, say 10?

This article will answer all these questions and help you understand the history behind our weekly calendar.

Where It All Started

The seven-day week originated from the Babylonian ancient civilization between 1000 and 2000 BC. The people living in Mesopotamia, modern-day Iran, were mainly astronomers and astrologers who were very interested in observing star movements. They were also involved in following the phases of the moon.

According to the observations made by these astronomers, they discovered that it usually takes around 28 days for the moon to cycle through all phases. This cycle explains why there are between 28 to 31 days in a month.

Since 28 days is too long to use as a measurement of time, it seemed impractical to use. They, therefore, resorted to breaking the 28 days into four periods of 7 days each. Babylonians were the most dominant culture in the Near East, which led to the entire region adopting this notion of time.

The Jews, who were under the Babylonians, adopted the seven days in a week calendar before it spread to the Greek and Persian empires.

Where Did the Names of the Days Come From?

The Babylonians were astute astrologers and astronomers. Their interest in observing the skies led to a horoscope that assigns each day to one of the classical planets.

These are the seven planets visible to the naked eye:
• Sun
• Moon
• Mars
• Mercury
• Jupiter
• Venus
• Saturn

However, it was the Romans who developed modern-day names years after the Babylonians introduced the seven-day calendar. The Romans initially used letters A to H to name the days. They later followed the path of the Greeks and Babylonians to name the days after their gods.

The Romans named days of the week after:
• Mars
• Mercury
• Jove
• Venus
• Saturn
• Moon
• Sun

The name origin for each day of the week has its roots in Roman mythology. The days were named after Roman gods and are directly related to names of planets, the sun, and the moon. The modern words used for each weekday in the Romance languages (e.g., Spanish, French, and Italian) are based on the Latin words that correspond to Roman gods (with the exception of Saturday and Sunday). However, while the English words for weekday names have Roman roots, the English names have been subjected to centuries of Germanic and Norse mythology. The Germanic people adapted the Roman system, switching out Roman deity names for German or Norse ones. The following is a list of the origin of the weekday names in the English language with notes on deviations and adaptations of the Romance languages:


sun sunday
© bigstockphoto.com / nature78


Sunday


Old English Sunnandæg, means literally, the sun's day. English, like most of the Germanic languages, preserves the day's association with the sun. However, the Romance languages have changed its name from associating it with the sun, to associating this day with "the Lord's day" (e.g., in Spanish the word for Sunday is “Domingo” meaning “of the Lord”).



moon monday
© bigstockphoto.com / dove13


Monday


Old English Mōnandæg, means the moon's day. This is similar to the Latin name dies lunae. The Romance languages have preserved Monday’s association with the moon. For example, in Spanish, Monday is called Lunes (the word moon is la luna in Spanish). Both names, Monday and Lunes, are associated with the moon.



mars tuesday
© bigstockphoto.com / alones


Tuesday


Old English Tīwesdæg, means Tiw's day. Tiw is a Norse war god (called Týr), but also the god who, more than any other, presides over matters of law and justice. Tiw also attested prominently in wider Germanic paganism. He seems equivalent to the Roman god Mars. Hence, the name of the day in the Romance languages is related to the Latin name dies Martis, "Day of Mars". In Spanish, for example, Tuesday is called Martes.



mercury wednesday
© bigstockphoto.com / Andrew Derr


Wednesday


Old English Wōdnesdæg, meaning the day of the Germanic god Woden (or Odin in Norse mythology). Woden was a supreme god and was widely known as a god of war. He was also important as a god of learning, of poetry, and of magic. He was a prominent god of the Anglo-Saxons and other Germanic peoples in England until about the seventh century. He was identified with the Roman god Mercury, and among Germanic peoples, Mercury's day became Woden's day (Wednesday). In Spanish, for example, Wednesday is called Miércoles (after Mercury).



jupiter thursday
© bigstockphoto.com / carlosramos


Thursday


Old English Þūnresdæg, meaning Thor's day. Thor is the hammer-wielding Norse god associated with thunder, lightning, storms, oak trees, strength, and the protection of mankind. He is also associated with sanctity and fertility. Thor's day corresponds to Latin dies Iovis, "day of Jupiter" or Jueves, in Spanish for example.



venus friday
© bigstockphoto.com / MediaWhalestock


Friday


Old English Frīgedæg, meaning the day of the Anglo-Saxon goddess Fríge (or the Norse goddess Frigg). Fríge was the goddess of love, marriage, and destiny. She was a sky goddess, responsible for weaving the clouds, sunshine, and rain which ultimately determined the fertility of the crops. She was also responsible for weavin fates. The Norse name for the planet Venus was Friggjarstjarna, 'Frigg's star'. It is based on the Latin dies Veneris, "Day of Venus". In the Romance languages, Friday is known as Viernes, Vendredi¸ and Venerdì in Spanish, French, and Italian respectively.



saturn saturday
© bigstockphoto.com / tovalex


Saturday


Named after the Roman god Saturn, it is the only day of the week that has retained its Roman origin in English. Its original Anglo-Saxon description was Sæturnesdæg. In Latin, it was dies Saturni, "Day of Saturn". Saturn is the Roman and Italic god of agriculture. Saturn ruled in a happy and innocent age, where he taught his people agriculture and other peaceful arts. In the Romance languages, Saturday is not associated with the Roman god; rather Saturday is associated with the day of the Sabbath. For example, Saturday is referred to as Sábado, Samedi, and Sabato in Spanish, French, and Italian respectively.



What Inspired the Order of the Days?

The order of days originated from ancient Rome. Roman astronomers observed how fast the classical planets crossed the sky and made the conclusion that the fastest object must be nearer to the earth. Following the same analogy, the objects that took longer to cross the sky were thought as farther from the earth.

Summary

The seven days of the week originated from the Babylonians’ lunar month, which is separated into four manageable chunks of seven days each. The names used currently developed over time as the Romans and Greeks named the days after their gods and goddesses.