Why do we have a seven day week?

[Kishan]

All over the world, in almost all cultures we have seven day weeks. The names may differ in various languages but a week always have seven days in them. Why is it so?

Most of the units of measurements of time are based on six. We have twelve(6x2) months in a year, 30(6x5) days in a month, 24(6x4) hours in a day, 60(6x10) minutes in an hour and 60(6x10) seconds in a minute. The week is the only unit of time measurement that is exception to this general pattern. Why? Why did a six day week not develop?

This seven day week not only stand out as an anomaly but also do not fit into the list of units well. If it was a six day week we could have counted as six days a week, five weeks a month and twelve months an year. But it's not possible with a seven day week.

 

[iori]

Because their are an uneven number of days in a year. p)

 

[Alex Richards]

It's down to the sidereal month. It takes approximately 28 days for the moon to reach the same position relative to the stars in her orbit of the earth. 28 is a rather unwieldy number, so it is divided in 4 to give 7 day weeks, a choice probably bolstered by the fact that the ancient world saw 7 heavenly bodies that were clearly not stars (Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn).

 

[ColeMercury]

Yeah, I think it may be due to the moon thing. You go from new moon to half moon to full moon to half moon to new moon again, week to week.

But seven-day weeks were never actually universal. They were just popular.

 

[Nugax]

All over the world, in almost all cultures we have seven day weeks. The names may differ in various languages but a week always have seven days in them. Why is it so?

...did you do any research before making this thread? Many cultures didn't have a 7 day week, instead having anything from 3 to 10 day weeks, but nearly everyone adopted it due to western dominance in the 19th and 20th century.

The seven day week is a ancient near-eastern innovation that became incorporated into Abrahamic tradition. Even the romans didn't officially switch to a seven day week until time of Constantine.

 

[Monte-Cristo]

The seven day week is a ancient near-eastern innovation that became incorporated into Abrahamic tradition

Indeed: the astrologers / astronomers of ancient Mesopotamia were struck by what, for them, could not be a coincidence, the 'obvious' division of the moon cycle in 4 phases of 7 days, and the presence of 7 moving 'stars' (the sun, moon, and the 5 interior planets) in the sky. Hence more generally the 7 tiers of the ziggurats, eventually through the Judaic tradition (e.g. the multiple occurrences of 7 and its compounds in the Book of Revelations) our 7 deadly sins, 7 colors, 7 notes in music &c...

 

[JennyB]

Indeed: the astrologers / astronomers of ancient Mesopotamia were struck by what, for them, could not be a coincidence, the 'obvious' division of the moon cycle in 4 phases of 7 days, and the presence of 7 moving 'stars' (the sun, moon, and the 5 interior planets) in the sky. Hence more generally the 7 tiers of the ziggurats, eventually through the Judaic tradition (e.g. the multiple occurrences of 7 and its compounds in the Book of Revelations) our 7 deadly sins, 7 colors, 7 notes in music &c...

The 'natural' order of the seven stars from a fixed earth outwards is: Moon Mercury Venus Sun Mars Jupiter Saturn. Assigning each in order to consecutive hours and repeating means that the first hour of each 24-hour day of 7-day week is named in our familiar sequence.

 

[Monte-Cristo]

The 'natural' order of the seven stars from a fixed earth outwards is: Moon Mercury Venus Sun Mars Jupiter Saturn. Assigning each in order to consecutive hours and repeating means that the first hour of each 24-hour day of 7-day week is named in our familiar sequence.

Is not our familiar sequence Moon-day, Mars-day, Mercurius-day, Jupiter-day, Venus-day, Saturn-day? In Germanic tongues (including English) and with some mistaken correspondences Moon-day, Tyr (or Thor)-day, Wotan-day, Donar (or Thor)-day, Friig (or Freija)-day...
Of course the medieval Church suggested an alternative etymology along the lines of martyrs-day for mars-day, but it was never taken seriously.

 

[Dionysius I]

The 'natural' order of the seven stars from a fixed earth outwards is: Moon Mercury Venus Sun Mars Jupiter Saturn. Assigning each in order to consecutive hours and repeating means that the first hour of each 24-hour day of 7-day week is named in our familiar sequence.

Isn't it Moon, Mars, Mercury, Jupiter, Venus, Saturn, Sun?

Italian: Lune-dì (Moonday), Marte-dì (Mars day), Mercoledì (Mercury day), Giove-dì (Jupiter day), Vener-dì (Venus day), Sabato (no but english Satur-day), Domenica (Dominus, no, but English Sunday)

 

[Kishan]

In Indian languages the weeks are generally named after Sun, Moon, Mars, Mercury, Jupiter, Venus and Saturn. In Sanskrit they are Bhanuvasara, Induvasara, Kujavasara, Budhavasara, Brihaspativasara, Shukravasara and Mandavasara. In Hindi they are Ravivar, Somavar, Mangalvar, Budhavar, Guruvar, Shukravar and Shanivar. In Malayalam Nhayar, Thingal, Chovva, Budhan, Vyazham, Velli and Shani. Tamil is similar. In all languages the days are named after Sun, Moon and five planets known in the ancient period.

 

[JennyB]

Isn't it Moon, Mars, Mercury, Jupiter, Venus, Saturn, Sun?

Italian: Lune-dì (Moonday), Marte-dì (Mars day), Mercoledì (Mercury day), Giove-dì (Jupiter day), Vener-dì (Venus day), Sabato (no but english Satur-day), Domenica (Dominus, no, but English Sunday)

Yes, that's the "familiar sequence" common to just about every European language. The other order I gave was that popularised by Ptolemy for the planetary spheres supposedly surrounding the earth - the basis for pre-modern astronomy and astrology. Other ancient authorities differed, for example placing the sphere of Venus outside that of the Sun.

Now, beginning at the closest sphere, the Moon, count one sphere for each hour, returning to Moon each time after Saturn. After 24 hours the next sphere will be Mars, so the next day is Mars-day, and so on. If the sphere of Venus were counted after that of the Sun, the order of days of the week would have been: Monday Tuesday, Wednesday, Thursday, Sunday, Saturday, Friday.

 

[Sicarius]

Interesting alternative examples: http://en.wikipedia.org/wiki/Soviet_calendar and http://en.wikipedia.org/wiki/French_revolutionary_calendar

 

[JennyB]

Isn't it Moon, Mars, Mercury, Jupiter, Venus, Saturn, Sun?

Italian: Lune-dì (Moonday), Marte-dì (Mars day), Mercoledì (Mercury day), Giove-dì (Jupiter day), Vener-dì (Venus day), Sabato (no but english Satur-day), Domenica (Dominus, no, but English Sunday)

Yes, that's the "familiar sequence" common to just about every European language. The other order I gave was that popularised by Ptolemy for the planetary spheres supposedly surrounding the earth - the basis for pre-modern astronomy and astrology. Other ancient authorities differed, for example placing the sphere of Venus outside that of the Sun.

Now, beginning at the closest sphere, the Moon, count one sphere for each hour, returning to Moon each time after Saturn. After 24 hours the next sphere will be Mars, so the next day is Mars-day, and so on. If the sphere of Venus were counted after that of the Sun, the order of days of the week would have been: Monday Tuesday, Wednesday, Thursday, Sunday, Saturday, Friday.

 

[viperhawkz]

Our days in English are derived from the Old English days Sunnandæg (Sun-day), Mōnandæg (Moon-day), Tiwesdæg (Tyr's day), Wōdnesdæg (Odin's day), Thūnresdæg (Thor's day), Frīġedæġ (Frigg's day), and the odd one out, Saeternesdaeg (Saturn's day).

 

[The Kiat]

Indeed: the astrologers / astronomers of ancient Mesopotamia were struck by what, for them, could not be a coincidence, the 'obvious' division of the moon cycle in 4 phases of 7 days, and the presence of 7 moving 'stars' (the sun, moon, and the 5 interior planets) in the sky. Hence more generally the 7 tiers of the ziggurats, eventually through the Judaic tradition (e.g. the multiple occurrences of 7 and its compounds in the Book of Revelations) our 7 deadly sins, 7 colors, 7 notes in music &c...

And let's not forget the whole made the world in six days and rested on the seventh from Hebrew mythology.

 

[Blackfox5]

The days of the week are named after the celestial objects that move in the sky.

Sun
Moon
Planet Mars (name of the war god in German is Tyr/Tiwaz/Tues)
Planet Mercury (Mercury was seen as same as the god Odin/Woden)
Plant Jupiter (Thor)
Planet Venus (Freya/Freia)
Planet Saturn

There is nothing inherent about the length of the week unlike the day (rotation of the earth), the month (cycle of the moon's phases) or the year (orbit around the sun).

7 days of a week probably came about because 28 days is approximate to the lunar cycle, and by having a 7 day week, you can easily divided up the month into 4 weeks then. And if you have a 7 day cycle, and you have 7 moving celestial objects, there is an obvious inspiration to name the days after.

 

[Carl Schwamberger]

Mayan calendar combined several cycles. One, a solar tracking calendar had a 360 day solar year divided into 20 day increments. A extra five day period was tagged onto the end of the 360 day year. The solar calendar overlapped a more complex 260 day cycle relating to fertility among other things; human pregnancy term is approx 260 days, growing season for several food plants of the Mayans was 260 days, ect... There are also connections between 260 days & some astronomical cycles recognized by the Maya astronomers.

I remember there was also a secondary Mayan calendaer with a 13 day increment.

 

[Turek]

I always thought it was because of the amount of days it took the Christian God to create the world (that's the book of Genesis, right?). Western culture's been heavily influenced by Christianity.

You guys have a point about the moon and stuff, though.

 

[Rex Mundi]

In this topic: everyone repeats the same information over and over again with varying levels of smugness.

 

[eliphas8]

Because the systems for recording time have always been disorganized messes that never really have "logical" units. I mean just look at our ridiculous misshapen months. Or the just strange system we use with leap years.