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A week is a unit of time equal to seven . 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 . 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 Rome, 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 Jews 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. Why Are There Seven Days in a Week?. Discover (15 January 2020). Retrieved 2022-10-22. 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 . Saturday has kept its Roman name, while the other six days use Germanic equivalents. Such a week may be called a planetary week (i.e., a classical planetary week). Certain weeks within a year may be designated for a particular purpose, such as Golden Week in China and Japan, and National Family Week in Canada. More informally, certain groups may advocate , 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 Geneva-based ISO standards organization 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 (work) week, while North America, South Asia, and many Catholic and Protestant countries, consider Sunday the first day of the week. It is also the first day of the week in almost all of the Arabic speaking countries. This is culturally and historically the case since in Arabic Sunday is referred to as "Yaom Al'Ahad" which literally means "The first day". Other regions are mixed, but typically observe either 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 (Shabbat) 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 Lord's Day), 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.
The seven-day week is named in many languages by a word derived from "seven". The archaism sennight ("seven-night") preserves the old Germanic practice of reckoning time by nights, as in the more common fortnight ("fourteen-night"). sennight at worldwidewords.org (retrieved 12 January 2017) Hebdomad and hebdomadal week both derive from the Koine Greek hebdomás (, "a seven"). Septimana is cognate with the Romance terms derived from Latin septimana]] ("seven mornings").
Slavic has a formation *tъdьnь (Croatian tjedan, Ukrainian , Czech týden, Polish tydzień), from *tъ "this" + *dьnь "day". Chinese has 星期]], as it were "planetary time unit". An older Chinese form is 禮拜]], meaning "week, religious ceremony."
In a Gregorian mean year, there are 365.2425 days, and thus exactly or 52.1775 weeks (unlike the Julian year of 365.25 days or ≈ 52.1786 weeks). There are exactly 20,871 weeks in 400 Gregorian years, so 03 August was a Sunday just as was 03 August 2025.
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 (letters A to G identifying the weekday of the first day of a given year) 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 (JD, i.e. the integer value at noon Universal Time): Adding one to the remainder after dividing the Julian day number by seven (JD modulo operation 7 + 1) yields that date's ISO 8601 day of the week. For example, the Julian day number of 03 August 2025 is . Calculating yields , corresponding to Sunday.Richards, E. G. (2013). "Calendars". In S. E. Urban & P. K. Seidelmann, eds. Explanatory Supplement to the Astronomical Almanac, 3rd ed. (pp. 585–624). Mill Valley, Calif.: University Science Books. 2013, pp. 592, 618. This is equivalent to saying that JD0, i.e. 1 January 4713 BCE of the proleptic Julian calendar, was a Monday. In 1973, John Conway devised the Doomsday rule for mental calculation of the weekday of any date in any year.
The ordering of the weekday names is not the classical order of the planets (by distance in the planetary spheres model, which is Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn; 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 CE, 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? (the text of Plutarch's treatise has been lost).E. G. Richards, Mapping Time, the Calendar and History, Oxford 1999. p. 269. Dio Cassius (early 3rd century) gives two explanations in a section of his Historia Romana after mentioning the Jewish practice of sanctifying the day called the day of Cronus (Saturday). Book 37, Sections 16-19. English translation.
| Saturday | |||||||
| Planet | Sun | Moon | Mars | Mercury | Jupiter | Venus | Saturn |
| Greco-Roman deity | Helios-Sol | Selene-Luna | Ares-Mars | Hermes-Mercury | Zeus-Iuppiter | Aphrodite-Venus | Cronus-Saturn |
| Koine Greek: | ἡμέρα Ἡλίου | ἡμέρα Σελήνης | ἡμέρα Ἄρεως | ἡμέρα Ἑρμοῦ | ἡμέρα Διός | ἡμέρα Ἀφροδίτης | ἡμέρα Κρόνου |
| Classical Latin: | dies Sōlis]] | dies Lūnae]] | dies Martis]] | dies Mercuriī]] | dies Iovis]] | dies Veneris]] | dies Saturnī]] |
| interpretatio germanica | — | ||||||
| sæterndæg | |||||||
| Indian religions Navagraha | Surya Sunday">Ravivar[[Ādityavāra | Sunday | Chandra
Chandra
Induvāsara | āra/ Saumyavāsara | Guruvāra/Bṛhaspativāsara | āra/ 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 (presumably via Gothic) the designation of Wednesday as "mid-week" in Old High German (mittawehha) and Old Church Slavonic (срѣда, srěda, literally, middle day). Old Church Slavonic may have also modeled the name of Monday, понєдѣльникъ (literally, the day after Sunday), after the Latin feria Secunda.Max Vasmer, Russisches etymologisches Wörterbuch, s.v. понедельник. However, the Slavic languages later introduced a secondary numbering system that names Tuesday as the "second day".
The ecclesiastical system became prevalent in Eastern Christianity, but in the Latin West it remains extant only in modern Icelandic, Galician, and Portuguese.the latter specifically due to the influence of Martin of Braga, 6th-century archbishop of Braga.
| "Seventh Day" or "Sabbath" (Saturday) | |||||||
| Byzantine 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/"day of ", i.e. the day before Sabbath, cf. Luke 23:54 (καὶ ἡμέρα ἦν Παρασκευῆς, καὶ σάββατον ἐπέφωσκεν.) | Σάββατον /sáb:aton/ |
| Latin | dies 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 language |
Gudea, the priest-king of Lagash in Sumer during the Gutian dynasty (about 2100 BCE), built a seven-room temple, which he dedicated with a seven-day festival. In the flood story of the Mesopotamia Epic of Gilgamesh, the storm lasts for seven days, the dove is sent out after seven days (similarly to Genesis), 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" (meaning inauspicious for certain activities). 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.
There are several hypotheses concerning the origin of the Old Testament seven-day cycle.
Friedrich Delitzsch and others suggested that the seven-day week being approximately a quarter of a lunation is the implicit astronomical origin of the seven-day week,
and indeed the Babylonian calendar used intercalary days to synchronize the last week of a month with the new moon.A month consisted of three seven-day weeks and the fourth week of eight or nine days, thus breaking the seven-day cycle every month. Consequently, there is no evidence that the days of the week were given individual names in Babylonian tradition. According to this theory, the Jewish week was adopted from the Babylonians while removing the moon-dependency.
George Aaron Barton speculated that the seven-day creation account of Genesis is connected to the Babylonian creation epic, Enûma Eliš, which is recorded on seven tablets."Each account is arranged in a series of sevens, the Babylonian in seven tablets, the Hebrew in seven days. Each of them places the creation of man in the sixth division of its series." cited after Albert T. Clay, The Origin of Biblical Traditions: Hebrew Legends in Babylonia and Israel, 1923, p. 74.
In a frequently-quoted suggestion going back to the early 20th century, the Hebrew Sabbath is compared to the Sumerian sa-bat "mid-rest", a term for the full moon. The Sumerian term has been reconstructed as rendered Sapattum or Sabattum in Babylonian, possibly present in the lost fifth tablet of the Enûma Eliš, tentatively reconstructed "Sabbath shalt thou then encounter, midmonthly".
However, Niels-Erik Andreasen, Jeffrey H. Tigay, and others claim that the Biblical Sabbath is mentioned as a day of rest in some of the earliest layers of the Pentateuch dated to the 9th century BCE at the latest, centuries before the Babylonian exile of Judah. They also find the resemblance between the Biblical Sabbath and the Babylonian system to be weak. Therefore, they suggest that the seven-day week may reflect an independent Israelites tradition. Tigay writes:
The seven-day week seems to have been adopted, at different stages, by the Persian Empire, in Hellenistic astrology, and (via Greek transmission) in Gupta India and Tang China.
The Babylonian system was received by the Greeks in the 4th century BCE (notably via Eudoxus of Cnidus). Although some sources, such as the Encyclopædia Britannica, state that the Babylonians named the days of the week after the five planets, the sun, and the moon, many scholars disagree. Eviatar Zerubavel says, "the establishment of a seven-day week based on the regular observance of the Sabbath is a distinctively Jewish contribution to civilization. The choice of the number 7 as the basis for the Jewish week might have had an Assyrian or Babylonian origin, yet it is crucial to remember that the ancient dwellers of Mesopotamia themselves did not have a seven-day week." The astrological concept of planetary hours is an innovation of Hellenistic astrology, probably first conceived in the 2nd century BCE.
The seven-day week was widely known throughout the Roman Empire by the 1st century CE, along with references to the Jewish Sabbath by Roman authors such as Seneca and Ovid. When the seven-day week came into use in Rome during the early imperial period, it did not immediately replace the older eight-day nundinal cycle system.
Frank Senn in his book Christian Liturgy: Catholic and Evangelical points to data suggesting evidence of an early continuous use of a seven-day week; referring to the Jews during the Babylonian captivity in the 6th century BCE, after the destruction of the Temple of Solomon.
While the seven-day week in Judaism is tied to Creation account in the Book of Genesis in the Hebrew Bible (where Elohim creates the heavens and the earth in six days and rests on the seventh; Genesis 1:1-2:3, in the Book of Exodus, the fourth of the Ten Commandments is to rest on the seventh day, Shabbat, which can be seen as implying a socially instituted seven-day week), it is not clear whether the Genesis narrative predates the Babylonian captivity of the Jews in the 6th century BCE. At least since the Second Temple period under Persian rule, Judaism relied on the seven-day cycle of recurring .
Tablets from the Achaemenid period indicate that the lunation of 29 or 30 days basically contained three seven-day weeks, and a final week of eight or nine days inclusive, breaking the continuous seven-day cycle.
The Babylonians additionally celebrated the 19th as a special "evil day", the "day of anger", because it was roughly the 49th day of the (preceding) month, completing a "week of weeks", also with sacrifices and prohibitions.
Difficulties with Friedrich Delitzsch's origin theory connecting Hebrew Shabbat with the Babylonian lunar cycle include reconciling the differences between an unbroken week and a lunar week, and explaining the absence of texts naming the lunar week as Shabbat in any language.
The ancient Romans traditionally used the eight-day nundinum but, after the Julian calendar had come into effect in 45 BCE, the seven-day week came into increasing use. For a while, the week and the nundinal cycle coexisted, but by the time the week was officially adopted by Constantine in 321 CE, the nundinal cycle had fallen out of use. The association of the days of the week with the Sun, the Moon and the five planets visible to the naked eye dates to the Roman era (2nd century).
The continuous seven-day cycle of the days of the week can be traced back to the reign of Augustus; the first identifiable date cited complete with day of the week is 6 February 60 CE, identified as a "Sunday" (as viii idus Februarius dies solis "eighth day before the ides of February, day of the Sun") in a Pompeiian graffito. According to the (contemporary) Julian calendar, 6 February 60 was, however, a Wednesday. This is explained by the existence of two conventions of naming days of the weeks based on the planetary hours system: 6 February was a "Sunday" based on the sunset naming convention, and a "Wednesday" based on the sunrise naming convention. Nerone Caesare Augusto Cosso Lentulo Cossil fil. Cos. VIII idus Febr(u)Arius dies solis, luna XIIIIX nun(dinae) Cumis, V (idus Februaries) nun(dinae) Pompeis.
The Chinese variant of the planetary system was brought to Japan by the Japanese monk Kūkai (9th century). Surviving diaries of the Japanese statesman Fujiwara Michinaga show the seven-day system in use in Heian Period Japan as early as 1007. In Japan, the seven-day system was kept in use for astrological purposes until its promotion to a full-fledged Western-style calendrical basis during the Meiji Period (1868–1912).
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.William Francis Ryan, The Bathhouse at Midnight: An Historical Survey of Magic and Divination in Russia, Penn State Press, 1999
p. 380.
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.William Francis Ryan, The Bathhouse at Midnight: An Historical Survey of Magic and Divination in Russia, Penn State Press, 1999
p. 383.
Sunday, in the ecclesiastical numbering system also counted as the feria prima or the first day of the week; yet, at the same time, figures as the "eighth day", and has occasionally been so called in Christian liturgy.
Justin Martyr wrote: "the first day after the Sabbath, remaining the first of all the days, is called, however, the eighth, according to the number of all the days of the cycle, and yet remains the first."
A period of eight days, usually (but not always, mainly because of Christmas Day) starting and ending on a Sunday, is called an octave, particularly in Roman Catholic liturgy. In German, the phrase heute in acht Tagen (literally "today in eight days") can also mean one week from today (i.e. on the same weekday). The same is true of the Italian phrase oggi otto (literally "today eight"), the French à huitaine, and the Spanish de hoy en ocho.
Examples:
Notes
Because the week starts on either Saturday, Sunday, or Monday in all these systems, the days in a workweek, Monday through Friday, will always have the same week number within a calendar week system. Quite often, these systems will agree on the week number for each day in a workweek:
Note that this agreement occurs only for the week number of each day in a work week, not for the day number within the week, nor the week number of the weekends.
The epi week ( epidemiological week) is used to report healthcare statistics, as with COVID-19 cases:
The tire date code mandated by the US DOT is a 4 digit date code WWYY with two digits of the week number WW followed by the last two digits of the calendar year YY.
An eight-day week was used in Ancient Rome and possibly in the pre-Christian Celtic calendar. Traces of a nine-day week are found in Baltic languages and in Welsh language. The ancient Chinese calendar had a ten-day week, as did the ancient Egyptian calendar (and, incidentally, the French Republican Calendar, dividing its 30-day months into thirds).
A six-day week was used in the Akan calendar and Kabye people culture in West Africa until 1981. Several cultures used a five-day week, including the Javanese calendar and the traditional cycle of market days in Korean culture. The Igbo have a "market week" of four days. Evidence of a "three-day week" has been derived from the names of the days of the week in Guipuscoan Basque. Astronomy and Basque Language, Henrike Knörr, Oxford VI and SEAC 99 "Astronomy and Cultural Diversity", La Laguna, June 1999. It references Alessandro Bausani, 1982, The prehistoric Basque week of three days: archaeoastronomical notes, The Bulletin of the Center for Archaeoastronomy (Maryland), v. 2, 16–22.
1. astelehena ("week-first", Monday), 2. asteartea ("week-between", Tuesday), 3. asteazkena ("week-last", Wednesday).
The Aztecs and Mayas used the Mesoamerican calendars. The most important of these calendars divided a ritual cycle of 260 days (known as Tonalpohualli in Nahuatl and Tzolk'in in Yucatec Maya) into 20 weeks of 13 days (known in Spanish as ). They also divided the solar year into 18 periods ( winal) of 20 days and five nameless days ( wayebʼ), creating a 20-day month divided into four five-day weeks. The end of each five-day week was a market day.
The Balinese Pawukon is a 210-day calendar consisting of 10 different simultaneously running weeks of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 days, of which the weeks of 4, 8, and 9 days are interrupted to fit into the 210-day cycle.
A 10-day week, called a décade, was used in Revolutionary France for nine and a half years from October 1793 to April 1802. The Paris Commune adopted this calendar for 18 days in 1871.
The Bahá'í calendar features a 19-day period that some classify as a month and others classify as a week.
From 1929 to 1951, five national holidays were days of rest (, , ). From autumn 1929 to summer 1931, the remaining 360 days of the year were subdivided into 72 five day work weeks beginning on . Workers were assigned any one of the five days as their day off, even if their spouse or friends might be assigned a different day off. Peak use of the five day work week occurred on at 72% of industrial workers. From summer 1931 until , each Gregorian month was subdivided into five six day work weeks, more-or-less, beginning with the first day of each month. The sixth day of each six day work week was a uniform day of rest. On 74.2% of industrial workers were on non-continuous schedules, mostly six day work weeks, while 25.8% were still on continuous schedules, mostly five day work weeks. The Gregorian calendar with its irregular month lengths and the traditional seven day week were used in the Soviet Union during its entire existence, including 1929–1940; for example, in the masthead of Pravda, the official Communist newspaper, and in both Soviet calendars displayed here. The traditional names of the seven day week continued to be used, including "Resurrection" (Воскресенье) for Sunday and "Sabbath" (Суббота) for Saturday, despite the government's official state atheism.
Judaism
A continuous seven-day cycle that runs throughout history without reference to the phases of the moon was first practiced in Judaism, dated to the 6th century BCE at the latest.
It is clear that among neighboring nations that were in position to have an influence over Israel – and in fact which did influence it in various matters – there is no precise parallel to the Israelite Sabbatical week. This leads to the conclusion that the Sabbatical week, which is as unique to Israel as the Sabbath from which it flows, is an independent Israelite creation.
(1983). 9782760347021, Editions de l'Universitá d'Ottawa. ISBN 9782760347021 The nundinal system had probably fallen out of use by the time Emperor Constantine adopted the seven-day week for official use in CE 321, making the Sunday (dies Solis) a legal holiday.
Achaemenid period
The Zoroastrian calendar follows the Babylonian in relating the 7th, 14th, 21st, and 28th of the 29- or 30-day lunar month to Ahura Mazda.Boyce, Mary (ed. & trans.). Textual Sources for the Study of Zoroastrianism. University of Chicago Press, 1984, p. 19-20.
The forerunner of all modern Zoroastrian calendars is the system used to determine dates in the Persian Empire, adopted from the Babylonian calendar by the 4th century BCE.
Hellenistic and Roman era
In Jewish sources by the time of the Septuagint, the term "Sabbath" () by synecdoche also came to refer to an entire seven-day week, Strong's Concordance, 4521. the interval between two weekly Sabbaths. Jesus's parable of the Pharisee and the Publican ( Luke 18:12) describes the Pharisee as fasting "twice in the week" (). In the account of the women finding the tomb empty, they are described as coming there "toward the one of the sabbaths" ();Matthew 28:1, Mark 16:2 translations substitute "week" for "sabbaths".
Islamic concept
According to Islamic beliefs, the seven-day a week concept started with the creation of the universe by Allah. Abu Hurayra reported that Muhammad said: Allah, the Exalted and Glorious, created the clay on Saturday and He created the mountains on Sunday and He created the trees on Monday and He created the things entailing labour on Tuesday and created light on Wednesday and He caused the animals to spread on Thursday and created Adam after 'Asr on Friday; the last creation at the last hour of the hours of Friday, i. e. between afternoon and night.
Adoption in Asia
China and Japan
The earliest known reference in Chinese writings to a seven-day week is attributed to Fan Ning, who lived in the late 4th century in the Jin dynasty, while diffusions from the Manichaeism are documented with the writings of the Chinese Buddhist monk Yi Jing and the Ceylonese or Central Asian Buddhist monk Amoghavajra of the 7th century (Tang dynasty).
India
The seven-day week was known in India by the 6th century, referenced in the Pañcasiddhāntikā. Shashi (2000) mentions the Yuga Purana, which he places in the 1st century BCE or CE, as a possible earlier reference to a seven-day week in India. He concludes "the above references furnish a terminus ad quem (viz. 1st century) The terminus a quo cannot be stated with certainty".
Christian Europe
The seven-day weekly cycle has remained unbroken in Christendom, and hence in Western history, for almost two millennia, despite changes to the Coptic calendar, Julian calendar, and Gregorian calendars, demonstrated by the date of Easter Sunday having been traced back through numerous computus to an Ethiopic copy of an early Alexandrian table beginning with the Easter of 311 CE.
Numbering
Weeks in a Gregorian calendar year can be numbered for each year. This style of numbering is often used in European and Asian countries. It is less common in the U.S. and elsewhere.
The ISO week date system
The system for numbering weeks is the ISO week date system, which is included in ISO 8601. This system dictates that each week begins on a Monday and is associated with the year that contains that week's Thursday.
Determining Week 1
In practice week 1 ( W01 in ISO notation) of any year can be determined as follows:
Week 52 and 53
It is also possible to determine if the last week of the previous year was Week 52 or Week 53 as follows:
Schematic representation of ISO week date
+ Dominical letter(s) plus weekdays, dates and week numbers at the beginning and end of a year
1. Numbers and letters in parentheses, ( ), apply to March − December in leap years.
2. Underlined numbers and letters belong to previous year or next year.
3. First date of the first week in the year.
4. First date of the last week in the year.
Other week numbering systems
In some countries, though, the numbering system is different from the ISO standard. At least six numberings are in use:
The epidemiological week begins on Sunday and ends on Saturday. The first epidemiological week of the year ends on the first Saturday of January, provided that it falls at least four or more days into the month. Therefore, the first epidemiological week may actually begin in December of the previous year.
Uses
The semiconductor package date code is often a 4 digit date code YYWW where the first two digits YY are the last 2 digits of the calendar year and the last two digits WW are the two-digit week number.
"Weeks" in other calendars
The term "week" is sometimes expanded to refer to other time units comprising a few days. Such "weeks" of between four and ten days have been used historically in various places.OED s.v. "week n.", entry 1.c.: "Sometimes applied transf. to other artificial cycles of a few days that have been employed various peoples" Intervals longer than 10 days are not usually termed "weeks" as they are closer in length to the fortnight or the month than to the seven-day week.
Pre-modern
Calendars unrelated to the Chaldean, Hellenistic, Christian, or Jewish traditions often have time cycles between the day and the month of varying lengths, sometimes also called "weeks".
Modern reforms
The International Fixed Calendar (also known as the "Eastman plan") kept a 7-day week while defining a year of 13 months with 28 days each (364 days). Every calendar date was always on the same weekday. It was the official calendar of the Eastman Kodak Company for decades.
Soviet
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.
See also
Notes
Further reading
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