A week is a period of seven days, a unit of time artificially devised with no astronomical basis.
1 week = 7 days = 168 hours = 10,080 minutes = 604,800 seconds.
In many languages, the days of the week are named after classical planets or gods of a pantheon.
In English, the names are Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday, then returning to Monday.
Monday is derived from Old English Mōnandæg and Middle English Monenday, originally a translation of Latin dies lunae “day of the Moon”.
Tuesday is derived from Old English Tiwesdæg and Middle English Tewesday, meaning “Tīw’s Day”, the day of Tiw or Týr, the god of single combat, and law and justice in Norse mythology.
Wednesday is derived from Old English Wōdnesdæg and Middle English Wednesdei, “day of Woden”, reflecting the religion practised by the Anglo-Saxons, the English equivalent to the Norse god Odin.
Thursday is derived from Old English þunresdæg and Middle English Thuresday meaning “Thor’s Day”. It was named after the Norse god of Thunder, Thor.
Friday comes from Old English frīġedæġ, meaning the “day of Frig”, a result of an old convention associating the Germanic goddess Frigg with the Roman goddess Venus, with whom the day is associated in many different cultures.
Saturday comes from Old English Sæterndæg – translation of Latin Saturni dies Sāturni diēs (“Saturn’s Day”) no later than the 2nd century for the planet Saturn, which controlled the first hour of that day, according to Vettius Valens.
Sunday comes from Old English Sunnandæg, which is derived from a Germanic interpretation of the Latin dies solis, “sun’s day.”
The English word “week” comes from the Old English wice, ultimately from a Common Germanic *wikōn-, from a root *wik- “turn, move, change”. The Germanic word probably had a wider meaning prior to the adoption of the Roman calendar, perhaps “succession series”, as suggested by Gothic wikō translating taxis “order” in Luke 1:8.
The week’s origin is generally associated with the ancient Jews and the biblical account of the Creation, according to which God laboured for six days and rested on the seventh.
Evidence indicates, however, that the Jews may have borrowed the idea of the week from Mesopotamia, for the Sumerians and the Babylonians divided the year into weeks of seven days each, one of which they designated a day of recreation.
Mesopotamian astrologers designated one day for each of the seven most prominent objects in the sky—the Sun, the Moon, and the five major planets visible to the naked eye.
Counting from the new moon, the Babylonians celebrated the 7th, 14th, 21st and 28th as “holy days”, also called “evil days”. On these days, officials were prohibited from various activities and common men were forbidden to “make a wish”, and at least the 28th was known as a “rest day”. On each of them, offerings were made to a different god and goddess.
In the flood story of the Assyro-Babylonian Epic of Gilgamesh, the storm lasts for seven days, the dove is sent out after seven days, and the Noah-like character of Utnapishtim leaves the ark seven days after it reaches the firm ground.
The Babylonians named each of the days after one of the five planetary bodies known to them (Mercury, Venus, Mars, Jupiter, and Saturn) and after the Sun and the Moon, a custom later adopted by the Romans.
Because the moon cycle is 29.53 days long, the Babylonians would insert one or two days into the final week of each month.
The Babylonian system was received by the Greeks in the 4th century BC. However, the designation of the seven days of the week to the seven planets is an innovation introduced in the time of Augustus.
The seven-day weekly cycle has remained unbroken in Christendom, and hence in Western history, for almost two millennia, despite changes to the Coptic, Julian, and Gregorian calendars, demonstrated by the date of Easter Sunday having been traced back through numerous computistic tables to an Ethiopic copy of an early Alexandrian table beginning with the Easter of 311 AD.
The Roman emperor Constantine I (died 337 AD), a convert to Christianity, introduced the first civil legislation concerning Sunday in 321, when he decreed that all work should cease on that day, except that farmers could work if necessary. That law, aimed at providing time for worship, was followed later in the same century and in subsequent centuries by further restrictions on Sunday activities.
A tradition of divinations arranged for the days of the week on which certain feast days occur develops in the Early Medieval period. There are many later variants of this, including the German Bauern-Praktik and the versions of Erra Pater published in 16th to 17th century England, mocked in Samuel Butler’s Hudibras. South and East Slavic versions are known as koliadniki (from koliada, a loan of Latin calendae), with Bulgarian copies dating from the 13th century, and Serbian versions from the 14th century.
Medieval Christian traditions associated with the lucky or unlucky nature of certain days of the week survived into the modern period. This concerns primarily Friday, associated with the crucifixion of Jesus. Sunday, sometimes personified as Saint Anastasia, was itself an object of worship in Russia, a practice denounced in a sermon extant in copies going back to the 14th century.
In some traditions of Christianity, Holy Week is the most sacred week in the Church year. In Eastern Rite Churches, also known as Eastern Orthodox, Holy Week occurs the week after Lazarus Saturday and starts on the evening of Palm Sunday. In the rites of the Western/Latin/Roman Church it begins with Palm Sunday and concludes on Easter Sunday. For all Christian traditions it is a moveable observance. In Eastern Rite Churches, Holy Week starts after 40 days of Lent and two transitional days, namely Saturday of Lazarus (Lazarus Saturday) and Palm Sunday. In Western Rite Churches, Holy Week falls on the last week of Lent or Sixth Lent Week.
In 1793 the leaders of the French Revolution produced a new calendar divided into three ten-day “decades.” It never caught on, and Napoleon abandoned it in 1805.
In the Soviet Union between 1929 and 1940, most factory and enterprise workers, but not collective farm workers, used five and six day work weeks while the country as a whole continued to use the traditional seven day week.