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A week is a time unit equal to seven days. It is the standard time period used for cycles of work days and rest days in most parts of the world.

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.[1] 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.


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.

Seven-day week[edit]

The Babylonian religion, from which Judaism's Genesis creation narrative stems, used a seven-day week.[2] Hence, evidence of continuous use of a seven-day week until today is to be found since the Babylonian Captivity of the Jews in the 6th century BC.[3] Roman Emperor Constantine adopted the seven-day week during the 4th century. The fate of the week in the next centuries was linked to the expansion of the Church, at the expense of pagan weeks.

Systems derived from the seven-day week[edit]

Soviet Union[edit]

Soviet calendar
12 December 1937
(Below 12:)
"Sixth day of the six-day week"
"Election day for the Supreme Soviet of the USSR"
Main article: Soviet calendar

Between 1929 and 1931 the USSR changed from the seven-day week to a five-day week. There were 72 weeks and an additional five national holidays inserted within three of them totaling a year of 365 days.[citation needed]

In 1931, after its brief experiment with a five-day week, the Soviet Union changed to a six-day week. Every sixth day (6th, 12th, 18th, 24th and 30th) of the Gregorian Calendar was a state rest day. The five additional national holidays in the earlier five-day week remained and did not fall on the state rest day. But as January, March, May, July, August, October and December have 31 days, the week after the state rest day of the 30th was seven days long (31st–7th). This extra day was a working day for most or an extra holiday for others. Also as February is only 28 or 29 days depending on whether it is a leap year or not, the first of March was also made a state rest day, although not every enterprise conformed to this. To clarify, the week after the state rest day, 24/25 February to 1 March, was only five or six days long, depending on whether it was a leap year or not. The week after that, 2 to 6 March, was only five days long.[citation needed]

The calendar was abandoned 26 June 1940 and the seven-day week reintroduced the next day.[citation needed]

Decimal calendar[edit]

A 10-day week, called décade, was used in France for nine and a half years from October 1793 to April 1802; furthermore, the Paris Commune adopted the Revolutionary Calendar for 18 days in 1871.

Christian "eighth day"[edit]

Main article: Octave (liturgical)

For early Christians, Sunday, as well as being the first day of the week, was also the spiritual eighth day, as it symbolised the new world created after Christ's resurrection. The concept of the eighth day was symbolic only and had no effect on the use of the seven-day week for calendar purposes. 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".[4] This does not set up an eight-day week, since the eighth day is also considered to be the first day of the next cycle (i.e., not the following day).

A period of eight days, starting and ending on a Sunday or starting on a major feast day and finishing on the same day of the week a (seven-day) week later, is called an octave. For centuries these were a major feature of the liturgical calendar, particularly of the Catholic Church, and some are still observed, though the number of such octaves has now been radically reduced. Some modern churches also preserve the idea of an eight-day period, starting and finishing on the same day of the week, and retain the name "octave" for them; for example, many churches observe an annual "Octave of Prayer for Christian Unity" on 18–25 January or in the week that begins with Pentecost Sunday. Organizations such as 8th Day Center for Justice, based out of Chicago, Illinois, use the concept in terms of social justice as well.

Hermetic lunar week[edit]

The Hermetic Lunar Week Calendar is one of many proposed reforms to the Gregorian Calendar. The lunation is divided into the four moon phases and has six, seven, eight, or nine days depending on the actual time difference between the full moon, first quarter, new moon and last quarter.[5]

"Weeks" in other calendars[edit]

Periods termed "weeks" in calendars unrelated to the Judeo-Christian tradition.


The names of the days of the week (aste) in Guipuscoan Basque point to an earlier three-day week.[6]

  1. astelehena ("week-first", Monday)
  2. asteartea ("week-between", Tuesday)
  3. asteazkena ("week-last", Wednesday)


The Igbo of Nigeria have a traditional calendar with a four-day week. This "market week" features prominently in the fiction of Chinua Achebe.


Main article: Javanese calendar

The Javanese people of Indonesia have a five-day week known as the Pasaran cycle. This is still in use today and superimposed with seven-day week of the Gregorian calendar and Islamic calendar to become what is known as the 35-day Wetonan Cycle.

In Korea, a five-day cycle of market days is still observed, and in the countryside was the usual reference for making appointments and marking time.

During the Viking Age, Scandinavians used a five-day week called a fimmt (from the Old Norse word for five). Each month had six fimmts, giving a year of 360 days, divided into twelve lunar months, each of 30 days, with four intercalary days (Auknætr), thus making 364 days; as the year was reckoned about the middle of the 10th century (the original calculation probably only reckoned 360 days, and made up the difference by irregular intercalary months). About the year 960 AD. Thorstein Surt introduced the sumarauki (intercalary week, 11 extra days), which was added to Auknætr, to be inserted every seventh year, thus bringing the year up to 365 days. After the introduction of Christianity (1000 AD) the sumarauki was made to harmonize with the Julian calendar; but from 1700 AD with the Gregorian calendar. It has been speculated that the name Tvímánudr ("two month", the month after the summer solstice) might point to an earlier system of intercalation in which this month was periodically doubled. It is also possible that Yule was originally a shorter period (cf. Norwegian Skammtid "short time" - unless that just refers to the shortness of daylight)[7]


Main article: Akan Calendar

The Akan people of West Africa have a 42-day cycle known as Adaduanan. The Adaduanan cycle appears to be based on an older six-day week, still extant in some northern Guan communities such as the Nchumuru, on which is superimposed a seven-day week which may have been brought south with itinerant traders from the Savannah.[8] The six-day week is referred to as Nanson (literally seven-days), reflecting an inclusive numbering system.

More recently, an Argentinean astronomer Carlos Varsavsky proposed a six day week, with society split into three groups working different weeks of four days followed by two rest-days in order to exploit national resources more efficiently with less human effort.


Further information: Burmese zodiac

In the Burmese version of Theravada Buddhism, the week has eight days. Wednesday is divided into Wednesday proper (midnight to noon) and Rahu (noon to midnight). Each day is associated with a compass direction, a planet, and a totem animal.

Nundinal cycle[edit]

The ancient Etruscans developed an eight-day market week known as the nundinal cycle around the 8th or 7th century BC. This was passed on to the Romans no later than the 6th century BC. As Rome expanded, it encountered the seven-day week and for a time attempted to include both. The popularity of the seven-day rhythm won and the eight-day week disappeared.

The cycle of seven days, named after the sun, the moon, and the five planets visible to the naked eye, was already customary in the time of Justin Martyr, who wrote of the Christians meeting on the Day of the Sun (Sunday).[9]

Emperor Constantine eventually established the seven-day week in the Roman calendar in AD 321.[10]


Further information: Celtic calendar

The Celts used periods of darkness such as night and winter to begin their calculations of time. This meant that the first period of time in a "week" was a night, followed by a day. Further, they also counted the ending night period, giving rise to periods of time with more nights than days. In Irish, the term nómad is used to signify a small number of days and is exactly the length of the nine night week as in co cend nomaide - a period of time with nine nights bracketing eight days. The nine nights divided nicely into a sidereal month of 27 nights. In Welsh a similar word wythnos meaning "a week" literally means "an eight-night" since it started and ended with a period of night bracketing seven days. Similarly a fortnight pythefnos means "a fifteen night".[11][12]


The Gediminas Sceptre, a medieval Lithuanian calendar. Showing 12 months and 9 days in a week

Baltic calendars[edit]

In the 14th century, the Grand Duchy of Lithuania used a solar-lunar calendar. The structure of this calendar was understood with the help of the so-called Gediminas Sceptre discovered in 1680.[13]

Similarly in Latvia petroglyphs were found in 1987, which are considered to show nine-day calendar with three weeks in a month.[14]

Archaeological evidence suggests that the week of the ancient Balts was nine days long. Thus, the sidereal month must have been divided into three parts.[15]

Medieval Welsh Calendars[edit]

Although the modern Welsh word for week refers to "eight nights", the Laws of Hywel Dda (in editions surviving from the 12th and 13th centuries) make repeated references to periods of nine days, instead, his month appearing to consist of three 'weeks' and a day.[16]


An occasional period of nine consecutive days of devotions, called a novena in Roman Catholicism, has no calendric significance.


China, Japan, Korea[edit]

The Chinese ten-day week went as far back as the Xia Dynasty (2070–1600 BC).[17] The law in the Han Dynasty (206 BC – AD 220) required officials of the empire to rest every five days, called mu (沐), while it was changed into 10 days in the Tang Dynasty (AD 618 – 907), called huan (澣/浣) or xún (旬). Months were almost three weeks long (alternating 29 and 30 days to keep in line with the lunation). The weeks were labelled shàng xún (上旬), zhōng xún (中旬), and xià xún (下旬) which mean roughly "upper", "middle" and "lower" week.

Markets in Japan followed the Chinese jun (旬) system; see Japanese calendar. In Korea, it was called "Sun" (순,旬).


Main article: Egyptian calendar

Ancient Egypt had a ten-day week, three weeks per month with five extra days at the end of the year.

Revolutionary France[edit]

In the French Republican Calendar, each month consisted of three ten-day weeks, called décades.

Other calendar intervals[edit]


Restored Aztec sun stone showing the 20 Days
Main article: Tonalpohualli

The Aztecs divided a ritual cycle of 260 days, known as Tonalpohualli, into 20 weeks of 13 days known as Trecena.

The Aztecs divided a solar year of 365 days, Xiuhpohualli, into 18 periods of 20 days and five nameless days known as Nemontemi. Although some call this 20-day division or grouping a month, it has no relation to a lunation. It was divided into four "weeks" of five days.[18]


Main articles: Tzolk'in and Maya calendar § Haab'

The Maya divided a 260-day ritual cycle known Tzolk'in into 20 weeks of 13 days known as Trecena.

The Maya also divided the year, Haab', into 18 periods of 20 days, Uinal, and five nameless days known as Wayeb'.

Bali, Indonesia[edit]

Main article: Pawukon

The Pawukon is a 210-day calendar consisting of 10 different concurrent weeks of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 days.

See also[edit]


  1. ^ 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"
  2. ^ Pinches, T.G. (2003). "Sabbath (Babylonian)". In Hastings, James. Encyclopedia of Religion and Ethics 20. Selbie, John A., contrib. Kessinger Publishing. pp. 889–891. ISBN 978-0-7661-3698-4. Retrieved 2009-03-17. 
  3. ^ Senn, Frank C. (1997). Christian Liturgy: Catholic and Evangelical. Fortress Press. ISBN 9780800627263. 
  4. ^ Dialogue with Trypho, chapter XLI
  5. ^ Meyer, Peter (2005-02-21). "Hermetic Lunar Week Calendar". Hermetic Systems. Retrieved 2009-01-21. 
  6. ^ 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.
  7. ^ http://www.oe.eclipse.co.uk/nom/calendar.htm#4
  8. ^ Bartle, Philip F.W. (1978). "Forty Days: The Akan Calendar". Africa: Journal of the International African Institute (Edinburgh University Press) 48 (1): 80–84. doi:10.2307/1158712. JSTOR 1158712. Retrieved 2009-01-21. 
  9. ^ Apology, chapter LXVII
  10. ^ Zerubavel, Eviatar (1989). The Seven Day Circle: The History and Meaning of the Week. University of Chicago Press. ISBN 9780226981659. 
  11. ^ Rhys (1840-1915), Sir John (1892). Lectures on the Origin and Growth of Religion as Illustrated by Celtic Heathendom. pp. 360–382. 
  12. ^ The Welsh people: chapters on their origin, history, laws, language ... - Sir John Rhys, Sir David Brynmor Jones - Google Books. p. 220. Retrieved 2012-10-22. 
  13. ^ Gusev, M. (1865). The Ancient Lithuanian Calendar (in Russian) 5. St. Petersburg: Izvestia of the Imperial Archaeological Society. p. 335. 
  14. ^ http://www.dabasretumi.lv/Raksti/GEnIdumejaRaksti.htm
  15. ^ Straižys, Vytautas; Klimka, Libertas. "Natural rythms and calendar". Cosmology of the Ancient Balts. Global Lithuanian Net. Retrieved 2009-01-21. 
  16. ^ Wade-Evans, Arthur. Welsh Medieval Laws. Oxford Univ., 1909. Accessed 31 Jan. 2013.
  17. ^ 海上 (2005). 《中國人的歲時文化》. 岳麓書社. p. 195. ISBN 7-80665-620-0. 
  18. ^ http://www.aztec-history.com/aztec-calendar-stone.html

Further reading[edit]

  • Colson, Francis Henry (1926). The Week: An Essay on the Origin and Development of the Seven-day Cycle. Cambridge University Press. OCLC 59110177. 

External links[edit]