Week
A week is a unit of time equal to seven days. It is the standard time period used for short cycles of days in most parts of the world. The days are often used to indicate common work days and rest days, as well as days of worship. Weeks are often mapped against yearly calendars. There are just over 52 weeks in a year. The term "week" may also be used to refer to a sub-section of the week, such as the workweek and weekend.
Ancient cultures had different "week" lengths, including ten days 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 due to the influence of the Christian seven-day week, which is rooted in the Jewish seven-day week. In AD 321, Emperor Constantine the Great 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.
In English, the names of the days of the week are Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday. In many languages, including English, the days of the week are named after gods or classical planets. Saturday has kept its Roman name, while the other six days use Germanic equivalents. Such a week may be called a planetary week. Certain weeks within a year may be designated for a particular purpose, such as Golden Week in China and Japan. More informally, certain groups may advocate awareness weeks, such as National Family Week in Canada, which are designed to draw attention to a certain subject or cause.
Cultures vary in which days of the week are designated the first and the last, though virtually all have Saturday, Sunday or Monday as the first day.
The three Abrahamic religions observe different days of the week as their holy day. Jews observe their Sabbath on Saturday, the seventh day, from sundown Friday to sundown Saturday, in honor of God's creation of the world in six days and then resting on the seventh. Most Christians observe Sunday, the first day of the week in traditional Christian calendars, in honor of the resurrection of Jesus. Muslims observe their "day of congregation", known as, on Friday because it was described as a sacred day of congregational worship in the Quran.
Name
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 seven-day week is named in many languages by a word derived from "seven". The archaism sennight preserves the old Germanic practice of reckoning time by nights, as in the more common fortnight. Hebdomad and hebdomadal week both derive from the Greek hebdomás. Septimana is cognate with the Romance terms derived from Latin wikt:septimana.
Definition and duration
A week is defined as an interval of exactly seven days, so that, except when passing through daylight saving time transitions or leap seconds,With respect to the Gregorian calendar:
- 1 Gregorian calendar year = 52 weeks + 1 day
- 1 week = ≈ 22.9984% of an average Gregorian month
Relative to the path of the Moon, a week is 23.659% of an average lunation or 94.637% of an average quarter lunation.
Historically, the system of dominical letters has been used to facilitate calculation of the day of week.
The day of the week can be easily calculated given a date's Julian day number :
Adding one to the remainder after dividing the Julian day number by seven yields that date's ISO 8601 day of the week. For example, the Julian day number of is. Calculating yields, corresponding to. In 1973, John Conway devised the Doomsday rule for mental calculation of the weekday of any date in any year.
Start and end
Cultures vary in which days of the week are designated the first and the last on their local calendars, though virtually all have Saturday, Sunday or Monday as the first day. The International Organization for Standardization uses Monday as the first day of the week in its ISO week date system through the international ISO 8601 standard. Most of Europe and China consider Monday the first day of the week, while North America, South Asia, and many Catholic and Protestant countries, consider Sunday the first day of the week. Other regions are mixed, but typically observe either Sunday or Monday as the first day. Many Arabic-speaking countries use Saturday as the first day of the week in calendar displays, while others use Monday or Sunday. The first day used in calendars may differ from the numbered 'name' of the day in a particular locale.Days of the week
The days of the week were named for the seven classical planets, which included the Sun and Moon. This naming system persisted alongside an "ecclesiastical" tradition of numbering the days in ecclesiastical Latin beginning with Dominica as the first day. The Greco-Roman gods associated with the classical planets were rendered in their interpretatio germanica at some point during the late Roman Empire, yielding the Germanic tradition of names based on indigenous deities.The ordering of the weekday names is not the classical order of the planets ; nor, equivalently, by their apparent speed of movement in the night sky. Instead, the planetary hours systems resulted in succeeding days being named for planets that are three places apart in their traditional listing. This characteristic was apparently discussed in Plutarch in a treatise written in c. 100 AD, which is reported to have addressed the question of Why are the days named after the planets reckoned in a different order from the actual order?. Dio Cassius gives two explanations in a section of his Historia Romana after mentioning the Jewish practice of sanctifying the day called the day of Kronos.
| Sunday | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | |
| Planet | Sun | Moon | Mars | Mercury | Jupiter | Venus | Saturn |
| Greco-Roman deity | Helios-Sol | Selene-Luna | Ares-Mars | Hermes-Mercury | Zeus-Jupiter | Aphrodite-Venus | Cronus-Saturn |
| Greek: | ἡμέρα Ἡλίου | ἡμέρα Σελήνης | ἡμέρα Ἄρεως | ἡμέρα Ἑρμοῦ | ἡμέρα Διός | ἡμέρα Ἀφροδίτης | ἡμέρα Κρόνου |
| Latin: | cat=0 | cat=0 | cat=0 | cat=0 | cat=0 | cat=0 | cat=0 |
| cat=0 | Sun | Moon | Tiwaz | Wodanaz | Þunraz | Frige | — |
| Old English | sunnandæg | mōnandæg | tiwesdæg | wōdnesdæg | þunresdæg | frīgedæg | sæterndæg |
| Indian Navagraha | Suryavāra/ Ravivāra/Bhānuvāsara/Ādityavāra | Chandravāra/ Somavāra/ Induvāsara | Mangalavāra/ Bhaumavāsara | Budhavāra/ Saumyavāsara | Guruvāra/Bṛhaspativāsara | Shukravāra/ Bhṛguvāsara | Shanivāra/ Sthiravāsara |
An ecclesiastical, non-astrological, system of numbering the days of the week was adopted in Late Antiquity. This model also seems to have influenced the designation of Wednesday as "mid-week" in Old High German and Old Church Slavonic. Old Church Slavonic may have also modeled the name of Monday, понєдѣльникъ, after the Latin feria Secunda.
The ecclesiastical system became prevalent in Eastern Christianity, but in the Latin West it remains extant only in modern Icelandic, Galician, and Portuguese.
| "First Day" or "Lord's Day" | "Second Day" | "Third Day" | "Fourth Day" | "Fifth Day" | "Sixth Day" | "Seventh Day" or "Sabbath" | |
| Greek | Κυριακὴ ἡμέρα /kiriaki iméra/ | Δευτέρα ἡμέρα /devtéra iméra/ | Τρίτη ἡμέρα /tríti iméra/ | Τετάρτη ἡμέρα /tetárti iméra/ | Πέμπτη ἡμέρα /pémpti iméra/ | Παρασκευὴ ἡμέρα /paraskevi iméra/ | Σάββατον /sáb:aton/ |
| Latin | dominica; rarely feria prima, feria dominica | feria secunda | feria tertia | feria quarta; rarely media septimana | feria quinta | feria sexta | Sabbatum; dies sabbatinus, dies Sabbati; rarely feria septima, feria Sabbati |
| Hebrew |
History
Ancient Near East
The earliest evidence of an astrological significance of a seven-day period is a decree of king Sargon of Akkad around 2300 BCE. Akkadians venerated the number seven, and the key celestial bodies visible to the naked eye numbered seven.Gudea, the priest-king of Lagash in Sumer during the Gutian dynasty, built a seven-room temple, which he dedicated with a seven-day festival. 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.
Counting from the new moon, the Babylonians celebrated the 7th, 14th, 21st and 28th of the approximately 29- or 30-day lunar month 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. Though similar, the later practice of associating days of the week with deities or planets is not due to the Babylonians.