Why are there 7 days in a week?

Question

Most things in the world are metric, using a base 10 decimal system. One major exception is the calendar, where there are 7 (not 10) days in a week. Why is that? Curious minds would like to know.

irifebeck · Accepted Answer

According to the internet:
Some of the earliest civilizations observed the cosmos and recorded the movements of planets, the Sun and Moon. The Babylonians in Mesopotamia, who lived in modern-day Iraq, were astute observers and interpreters of the heavens, and it is largely thanks to them that our weeks are seven days long.

The reason they adopted the number seven was that they observed seven celestial bodies — the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn. So, that number held particular significance to them.

Other civilizations chose other numbers — like the Egyptians, whose week was 10 days long; or the Romans, whose week lasted eight.

The Babylonians divided their lunar months into seven-day weeks, with the final day of the week holding particular religious significance. The 28-day month, or a complete cycle of the Moon, is a bit too large a period of time to manage effectively, and so the Babylonians divided their months into four equal parts of seven.

The Babylonians were such a dominant culture in the Near East, especially in the sixth and seventh centuries B. C., that this, and many of their other notions of time — such as a 60-minute hour — persisted.

The seven-day week spread throughout the Near East. It was adopted by the Jews, who had been captives of the Babylonians at the height of that civilization’s power. Other cultures in the surrounding areas got on board with the seven-day week, including the Persian empire and the Greeks.

Centuries later, when Alexander the Great began to spread Greek culture throughout the Near East as far as India, the concept of the seven-day week spread as well. Scholars think that perhaps India later introduced the seven-day week to China.

Finally, once the Romans began to conquer the territory influenced by Alexander the Great, they too eventually shifted to the seven-day week. It was Emperor Constantine who decreed that the seven-day week was the official Roman week and made Sunday a public holiday in A. D. 321.

Sour-rose · Accepted Answer

Okay, so I can answer this the boring way buuuut...

So let's say we get 9 days. Mon-sun then Malday, Furaday, and talday.

Malday-The day you work at home with your kids and it's the law that you work. You don't come into the office at all and you get free treats depending on your state.

Furaday- The day you must exercise for 3 hours. You still gotta work at home but it's mostly meetings and stuff. Again, the law... by now you tired and wish you could work at the office. You do, and security might punch you for breaking the law.

Talday-like Sunday until 6 o clock. You now have to do an hour of work and prepare your kids (if you have any) for school tomorrow.

Do we need such those days? I think not. :D Just make the week longer for some.

NamerOfStars · Accepted Answer

Mostly base ten? Like our 31-day months, our 24-hour days, and our 365-day years? The use of base ten only seems omnipresent because you're used to it; base 2 is more natural, base 6 is more common (or used to be), and base 12 is more useful. Interestingly, the Egyptian week DID have ten days- the Romans had eight, and the Aztecs had twenty; the seven we use comes from the Babylonians.

If you know anything about Babylonian numerology, this may seem very strange- not least because most of what we know today about Babylonian numerology is filtered through the lens of Israelite numerology, and gets a rather dark tinting because of that, but this was purely astronomical- the Babylonians saw the five "fixed stars" (Mercury, Venus, Mars, Jupiter, and Saturn), plus the sun and the moon, and used that as the base. Many people will tell you it's just dividing a 28-day lunar cycle into four even pieces, but the lunar cycle varies between 28.5 and 29.5 days, so that would add up inaccuracy VERY fast.

OlderAndWiser · Accepted Answer

Would you really prefer to wait 8 days for the weekend to get here?

bolverk · Answer

The modern seven-day week can be traced back to the Babylonians, who used it within their calendar. Other ancient cultures had different week lengths, including ten in Egypt and an eight-day week for Etruscans. The Etruscan week was adopted by the Ancient Romans, but they later moved to a seven-day week, which had spread across Western Asia and the Eastern Mediterranean. In 321 AD, Emperor Constantine officially decreed a seven-day week in the Roman Empire, including making Sunday a public holiday. This later spread across Europe, then the rest of the world.

FireGodGoesSeeknFire · Answer

It matches the 4 phases of the moon. A month is supposed to be one lunar cycle and a week one of the four phases in that cycle.

But there is no way to get the moon cycles and sun cycles to precisely align. Our modern society having to pick one date, day and time to universally represent each moment chose to make the Sun cycle more fundamental.

So now old lunar cycle measures are just hanging out without a precise link to anything.

genericname85 · Answer

i guess cause the ammount of days that fit in a year just aren't decimal, so they just gave up and left the pagan 7 day week that was already established in most places.

it's not like temperature. you don't you have a spectrum where you can freely choose the scale to fit a decimal system. earth just happens to revolve 365 times around it's own axis, while it's making one lap around the sun. it's impossible to have a decimal system that lines up with the day and the year cycle.

MountAverage · Answer

The decimal system is irrelevant here though. Seconds, minutes, days, months, and years - they're all decimal, but they're all based on natural phenoma (decay of atoms and orbital cycles of the Earth and the Moon). But you're right that it is still weird, since weeks are the only odd one out, not being based on anything astronomical or atomic. I guess you'll have to look into the history of weeks and why that system stuck.

jennifer_bloom · Answer

I believe the human body was not designed for 10 or 8 day work weeks, we were created to operate in cycles of 7. Phone numbers have 7 digits cause the average brain is able to remember 7 digits. 8 might be too many and 6 is too easy.

Amy10223 · Answer

It was based on the Babylonian calender, who based their weekday on the celestial bodies that were seen at that time. The sun, moon, Venus, Mercury, Jupiter ands Mars were all visible to them then.

purplepoppy · Answer

It's supposed to be because they could only see 7 planets back in the day. But for quite a while in the uk and probably parts of Europe you'd count nights as well as days just to make things complex.

ZXCwWRQWz · Answer

It was based on observable celestial bodies and relatively primitive astronomy to my understanding and tied to empirical observations rather than a neat mathematical system.

exitseven · Answer

I thought it was because it took God 6 days to create the world and he took Sunday off.

SnowedIn · Answer

Such a great question. @purplepoppy got one of the answers that I recall and it was the ability to see 7 celestial bodies. Astrologically, the ancients then devised it as roughly 1/4 of a moon cycle and went from there.

Cubus · Answer

I believe the ancient people decided that 7 days a week is the best, after errors and mistakes.

HippieVeganJewslim · Answer

Seven is a quarter of a perfect number. 28=14+7+4+2+1. One lunar month is close to 28 days.

shortster · Answer

According to the bible God created the universe in 6 days and rested on the seventh.

Adaeva · Answer

Because in the Bible, God rested on the 7th day.

fembotnpc777 · Answer

Why is the weather so nice today? How are you b e i n g?

CuriousMufuxka · Answer

Because 5 would only be work and 10 would have too much a break inbetween and vacation days and sick time and.. Yeah I dunno.

Guy13 · Answer

The Bible.

jimmy2 · Answer

Well so far so good 😂

Phoenix98 · Answer

Because 8 is to long and 6 isn’t enough.

Twalli · Answer

We also have a base 12 hour system

Why are there 7 days in a week?

Most Helpful Opinions

What Girls & Guys Said

Why are there 7 days in a week?

Most Helpful Opinions

What Girls & Guys Said

We're glad to see you liked this post.