The week, to which we are all enslaved, has a strange and erotic history

WHY does The Economist appear every seventh day? The answer is because we, like you, still regulate our lives by a septimal law that Mesopotamian star-gazers framed, and local warlords imposed, more than 40 centuries ago. Our weekdays and weekends and weeks off, our dress-down Fridays, hectic Saturday nights, Sundays sacred or profane, and Monday-morning blues all have their origin in something that happened around 2350BC. Sargon I, King of Akkad, having conquered Ur and the other cities of Sumeria, then instituted a seven-day week, the first to be recorded.

Ur was probably using weeks, less formally, long before Sargon came marching in. The Sumerians were great innovators in matters of time. It is to them, ultimately, that we owe not only the week but also the 60-minute hour. Such things came easily to people who based their maths not on a decimal system but on a sexagesimal one.

Why were these clever chaps, who went for 60 because it is divisible by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30, fascinated by stubbornly indivisible seven? In ancient Egypt and ancient China, “weeks” of ten days were long in use—much more understandable, as people have ten fingers to count on, not seven. (And yet you have to wonder, if the Pharaohs' long week was intended to drive their workforce harder, whether it provoked the Exodus?)

Above all, why should the Sumerian system have not merely endured but become an almost universal conqueror? Ur's posterity now sways regions Sargon never knew. Its lead has been slavishly followed by Babylonians, Greeks, Romans, Hindus ancient and modern, Muslims and most of the present inhabitants of Europe and the Americas. Even China surrendered a good thousand years ago.

The year, the day and (not quite so obviously) the month are natural divisions of time. The week is an oddity. The moon's four phases are a near miss, but still a misfit, for weeks. You will be in trouble (like H.G. Wells's “The Man Who Could Work Miracles”) if you try to make the moon perform every 28 days, instead of its usual 29½ and a bit. The Sumerians had a better reason for their septimalism. They worshipped seven gods whom they could see in the sky. Reverently, they named the days of their week for these seven heavenly bodies.

So do most of us today. Greeks, Slavs, and many Jews and Muslims, although loyal to Ur's seven-day week, have shaken off its planet-gods; but a great majority of Christians and of Hindus, and virtually all “unbelievers”, still pay their respects daily to the Sumerian seven—under changed names, of course.

For the Sumerians themselves, seven was a very special number. They conceived of a seven-branched Tree of Life, and of seven heavens, that were passed to Babylon and symbolised there in seven-tiered ziggurats, or hanging gardens. Sumeria's Gilgamesh epic describes the rite of passage through which Enkidu the ape-man became human, thanks to the obliging Shamhat:

In spite of all that, Ur's seventh day was not holy. On the contrary, it represented danger and darkness. It was risky to do anything at such a time. So it became a day of rest.

Ever since the time when Abraham trekked westward from Ur, Mesopotamian influences had helped to form Hebrew traditions. The Jews got the story of the Flood from Sumeria. They got the seven-day-week idea early enough to use it in the account of the Creation given in Genesis. But there may have been some garbling in the transmission. The Sumerians would not have depicted the Creator as just sitting back, satisfied, on the seventh day; to them, he would seem to have stopped work, wisely, because anything attempted on that day must end in tears. The week reached India from Mesopotamia more than 2,000 years ago, in time to get into some of the Hindu scriptures. But the Hindus' creation stories were far more complex than Hebrew ones. They never accepted a Sabbath; their scriptural references to the week, as in the Brahmavaivarta Purana, were almost casual:

The Hindus were keen sky-watchers and sometimes keen septimalists. They had noted the Pleiades (Krttikas). Noting also the Great Bear's seven stars, they identified them with the Seven Sages who survived the Flood, combined these starry sevens, and made the Pleiades the wives of the Sages. Yet, in their absorbent way, they happily adopted the seven planet-gods who arrived with the original Sumerian week. And, in their retentive way, they held on to them. In modern Hindi, as in ancient Sanskrit, the planets we call Mars and Mercury are Mangal and Budh. The days called Tuesday and Wednesday in English, and mardi and mercredi in French, are Mangalvar and Budhvar.

Elsewhere, new names have been showered on the old gods and their planets. Yet, to an astonishing extent, they have retained their identities—and kept their places in the order of the days of the week.

Enter Ishtar and Venus

The first recorded change came when the Sumerian week-system was transposed into the Semitic language spoken in the Babylonian empire. The day-names used in Babylon around 700BC (running as if from our Sunday to our Saturday) were: Shamash (Sun), Sin (Moon), Nergal (god of war), Nabu (god of scribes), Marduk (supreme god), Ishtar (goddess of love) and Ninurta (god of farming). They had simply replaced their Sumerian predecessors; for example, Ishtar had succeeded Inanna both as a planet and as the presiding deity of love.

By the time the Romans had adopted the system, the planet-gods wore names more familiar to us: (in the same order) Sol, Luna, Mars, Mercurius, Jupiter, Venus, Saturnus. But their identities remained almost intact. The name-chain Inanna-Ishtar-Astarte-Aphrodite had led to Venus. Nergal lived on in Mars. Aptly, the god of scribes had mutated into the heavenly messenger, Mercurius.

In English and the other Germanic languages, Mars, Mercurius, Jupiter and Venus were, in time, renamed in honour of Teutonic gods. From Tiw, Woden, Thor and Freya came the names of our weekdays from Tuesday to Friday. Even so, the chain remained unbroken. Although English Wednesday and Scandinavian Onsdag salute the god Woden or Odin, this came about only because he was identified with Mercurius. Similarly, the love-goddess Freya took the place of Venus—and her place in the weekly sequence.

Among Europe's Romance and Celtic languages, the Ur-idea of naming days from planet-gods is obvious. Mercurius is as recognisable in the French mercredi as in Romanian Mercuri or Welsh Mercher. The Slav languages, however, taking a lead from Greek, prefer numbering systems. (Five, in Russian, is pyat; Friday is Pyatnitsa. In Greek, Monday, Tuesday and Wednesday are Deutera, Triti and Tetarti; i.e., second, third and fourth.)

Saturnus, alone among the planet-gods, resisted Germanisation. And Saturday was “different” from other weekdays long before the two-day weekend developed. In ancient Rome it became somewhat inauspicious. Then it was, for a time, the Sabbath, both for Jews and for many early Christians. It is still Sabato in Italian, Sabado in Spanish, Sobota or Subota in the Slav languages.

Over the naming of Sunday some confusion has crept in, for which Constantine the Great is much to blame. In 321AD, when he ordered the cities of his empire to rest on this day, his edict was related to the sun, rather than to Christianity. Three centuries earlier, Augustus had officially recognised the week, with its Sumerian-style planet-gods. Dies solis, the sun's day, was mildly auspicious, but only the Christians made it really special as their day for congregational prayer, linked with the Resurrection and called the Lord's Day. Constantine chose to boost that day while invoking not Christ but the Unconquered Sun (the emperor himself, at that point, saw the two deities as one). He thereby gratified Christians without offending sun-worshippers.

So it was a shrewd move, at the time. But it left the naming of the day in schism. In its Germanic versions it is now strictly the Sun's day (Sonntag, Zonday, etc). But it is given to the Lord (Latin dominus, Greek kyrios) in Romance languages (Domingo, Domenica, dimanche) and Greek (Kyriaki), and the Celts are split, Welsh Dydd Sul confronting Gaelic De Domhnaich.

Most striking of all Sunday's names is the Russian Voskresenye (“Resurrection”), which endured through long years of imposed atheism. Do not imagine that Sumeria's week and its day-names have never faced any challenges. The French Revolution brought in a ten-day “week” whose days were, literally, numbered (the experiment lasted, officially, for 12 years, but never really took). As soon as the Bolsheviks seized power in Russia in 1917 they tried, but failed, to imitate the French revolutionaries (or the Pharaohs?). Later, for 11 years starting in 1929, Stalin imposed first five-day and then six-day weeks on the Soviet Union. The elimination of Sunday, with its strong religious associations, was one purpose of his experiments. They all failed, abjectly. Warned by this, the communist regimes established in other countries after 1945 did not even try to tamper with the Ur-old seven-day week.

Today, Sumeria's 4,400-year-old feat of cultural imperialism is triumphantly intact and more assured of universal acceptance than ever. How can this be explained? Seven is a thoroughly awkward number. It gives us a year of 52 weeks (another awkward number), plus the annoying extra one or two days which force us to keep buying new calendars.

The seven-day system's ability to challenge and, in time, overlay all others has always rested on its religious inspiration, not on its practical value. It has leapt blithely from one religious base to another, from Ur of the Chaldees to Israel, then on to Christendom, to Islam. It infiltrated the Roman empire before Christianity and reached India many centuries before the first Muslim invaders. European colonisers spread it through the Americas, but in the Old World, wherever Hindu or Muslim influences had penetrated, even the earliest European explorers found it was there before them.

Today, most of the human race takes it for granted that their activities are recorded in weeks. There are two groups: those who feel that the week has real religious significance and that there is something holy about one day in seven, and those who have no such feeling. In neither group will you find many people who know how the week came into existence, or came to matter.

“Men of old” knew. They could read it in the heavens. In a song of great antiquity like “Green grow the rushes O”, it was natural, perhaps unavoidable, to include the line “Seven for the seven stars in the sky”.

They are all still there: Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn. We may send out spacecraft to ring them round, but we ourselves are still held in the hebdomadal grip of the Seven.