The names of the days of the week from the Roman period have been both named after the seven planets of classical astronomy and numbered, beginning with Sunday. In Slavic languages, a numbering system was adopted, but beginning with Monday. There was an even older tradition of names in Ancient Indian Astrology which could arguably be the origin of all these naming systems. All of these systems was adopted in many languages, with some exceptions resulting from a number of religious and secular considerations.

Weekdays named after planets

[edit] History

Weekday heptagram

The order of the week days can be derived “geometrically” from an acute heptagram, the {7/3} star polygon (as 24 mod 7 = 3). The luminaries are arranged in the same Ptolemaic/Stoic order around the points of the heptagram. Tracing the unicursal line from one planet to the next gives the order of the weekdays.

This weekday heptagram is a development of Hellenistic astrology, and probably dates to the Roman era.^[1]

Between the 1st and 3rd centuries the Roman Empire gradually replaced the eight day Roman nundinal cycle with the seven-day week. The astrological order of the days was explained by Vettius Valens and Dio Cassius (and Chaucer gave the same explanation in his Treatise on the Astrolabe). According to these authors, it was a principle of astrology that the heavenly bodies presided, in succession, over the hours of the day. The Ptolemaic system asserts that the order of the heavenly bodies, from the farthest to the closest to the Earth, is: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. (This order was first established by the Greek Stoics.)

In astrological theory, not only the days of the week, but the hours of the day are dominated by the seven luminaries. If the first hour of a day is dominated by Saturn (), then the second hour is dominated by Jupiter (), the third by Mars (), and so on with the Sun (), Venus (), Mercury (), and the moon (), so that the sequence of planets repeats every seven hours. Therefore, the twenty-fifth hour, which is the first hour of the following day, is dominated by the Sun; the forty-ninth hour, which is the first hour of the next day, by the Moon. Thus, if a day is labelled by the planet which dominates its first hour, then Saturn’s day is followed by the Sun’s day, which is followed by the Moon’s day, and so forth, as shown below.

According to Vettius Valens, the first hour of the day began at sunset, which follows Greek and Babylonian convention. He also states that the light and dark halves of the day were presided over by the heavenly bodies of the first hour of each half. This is confirmed by a Pompeian graffito which calls 6 February 60 a Sunday, even though by modern reckoning it is a Wednesday. Thus this graffito used the daylight naming convention of Valens whereas the nighttime naming convention of Valens agrees with the modern astrological reckoning, which names the day after the ruler of the first daylight hour.

These two overlapping weeks continued to be used by Alexandrian Christians during the 4th century, but the days in both were simply numbered 1–7. Although names of gods were not used, the week beginning on Wednesday was named in Greek ton theon ([day] of the gods), as used by the late fourth-century editor of the Easter letters of Bishop Athanasius, and in a table of Easter dates for 311–369 that survives in an Ethiopic copy. These overlapping weeks are still used in the Ethiopic computus. Each of the days of the week beginning on Sunday is called a “Day of John” whereas each of the days of the week beginning on Wednesday is called a “tentyon”, a simple transcription of the Greek ton theon.

Hour:	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	Stellar Object → Day
Day 1																									Saturn → Saturday
Day 2																									Sun → Sunday
Day 3																									Moon → Monday
Day 4																									Mars → Tuesday
Day 5																									Mercury → Wednesday
Day 6																									Jupiter → Thursday
Day 7																									Venus → Friday

[edit] Indian astrology

This was probably the oldest and the most original tradition which traveled through ambassadors to the Near East and beyond into Europe. This forms the basis of week day names in most Indian languages and the languages of South Asia and South East Asia.

Though the explanation on the sequence of the name is only available in ancient texts in India. Which goes as below,

The division of days among the planets was done based on the speed of each planet as perceived from earth. Sun and Moon being the nearest and most important planets were allotted first two days and then the planet next in sequence to the original position of the planet was given the next day.. The sequence based on speed is Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn.

So after Sunday and Monday, the next to Sun was Mars hence the day was ‘Mangalwar’, next to moon was Mercury and hence ‘Budhawar’ next Mars was Jupiter and hence Guruwar , next to Mercury was Venus and hence ‘Shukrawar’ , next to Jupiter was Saturn and hence ‘Shaniwar’ and thus the seven names in this particular sequence.

[edit] Greco-Roman tradition

The earliest attestation of a seven day week associated with heavenly luminaries are from Vettius Valens, an astrologer writing ca 170 AD in his Anthologiarum. The order was Sun, Moon, Ares, Hermes, Zeus, Aphrodite, and Cronos. From Greece the planetary week names passed to the Romans, and from Latin to other languages of southern and western Europe, and to other languages later influenced by them.

Day: (see Irregularities)	Monday Luna (English: Moon)	Tuesday Mars (Mars)	Wednesday Mercurius (Mercury)	Thursday Iuppiter (Jupiter)	Friday Venus (Venus)	Saturday Saturnus (Saturn)	Sunday Sōl (Sun)
Ancient Greek	ἡμέρα Σελήνης heméra Selénes	ἡμέρα Ἄρεως heméra Áreos	ἡμέρα Ἕρμου heméra Hérmou	ἡμέρα Διός heméra Diós	ἡμέρα Ἀφροδίτης heméra Aphrodítes	ἡμέρα Κρόνου heméra Krónou	ἡμέρα Ἡλίου heméra Helíou
Latin	dies Lūnae	dies Martis	dies Mercuriī	dies Jovis	dies Veneris	dies Saturnī	dies Sōlis
Italian	lunedì	martedì	mercoledì	giovedì	venerdì	sabato [♄1]	domenica [☉1]
Spanish	lunes	martes	miércoles	jueves	viernes	sábado [♄1]	domingo [☉1]
Romanian	luni	marţi	miercuri	joi	vineri	sâmbătă [♄1]	duminică [☉1]
French	lundi	mardi	mercredi	jeudi	vendredi	samedi [♄1]	dimanche [☉1]
Galician	luns	martes	mércores	xoves	venres	sábado [♄1]	domingo [☉1]
Catalan	dilluns	dimarts	dimecres	dijous	divendres	dissabte [♄1]	diumenge [☉1]
Friulian	lunis	martars	miercus	joibe	vinars	sabide [♄1]	domenie [☉1]
Interlingua	Lunedi	Martedi	Mercuridi	Jovedi	Venerdi	Sabbato [♄1]	Dominica [☉1]
Ido	Lundio	Mardio	Merkurdio	Jovdio	Venerdio	Saturdio Ido dicationary	Sundio
Esperanto	lundo	mardo	merkredo	ĵaŭdo	vendredo	sabato [♄1]	dimanĉo [☉1]
Irish	An Luan Dé Luain	An Mháirt Dé Máirt	An Chéadaoin [☿2] Dé Céadaoin	An Déardaoin [♃1] Déardaoin	An Aoine [♀1] Dé hAoine	An Satharn Dé Sathairn	An Domhnach [☉1] Dé Domhnaigh
Scots Gaelic	Di-Luain	Di-Màirt	Di-Ciadain [☿2]	Di-Ardaoin [♃1]	Di-Haoine [♀1]	Di-Sàthairne	Di-Dòmhnaich [☉1]
Welsh	dydd Llun	dydd Mawrth	dydd Mercher	dydd Iau	dydd Gwener	dydd Sadwrn	dydd Sul
Cornish	Dy Lun	Dy Meurth	Dy Mergher	Dy Yow	Dy Gwener	Dy Sadorn	Dy Sul
Breton	Di’lun	Di’meurzh	Di’merc’her	Di’riaou	Di’gwener	Di’sadorn	Di’sul
Manx	Jelune	Jemayrt	Jecrean	Jerdrein	Jeheiney	Jesarn	Jedoonee [☉1]
Albanian	E hënë	E martë	E mërkurë	E enjte	E premte	E shtunë	E diel
Tagalog	Lunes	Martes	Miyerkules	Huwebes	Biyernes	Sabado [♃1]	Linggo [☉1]

[edit] Gaelic-Irish traditions

In pre-Christian Gaelic-Irish society, time was measured in “one-, three, five-, ten-, or fifteen-day periods; the seven-day week was entirely unknown.” (Dáibhí Ó Cróinín, 2003, p. 7). MS. 17, dating from at least 1043, is now held at St. John’s College, Oxford. It records five week-day lists, which it names as follows: secundum Hebreos (‘Hebrew’ days); secundum antiquos gentiles (Roman days of the week);secundum Siluestrum papam (a list derieved from the apocryphal Acta Syluestri); secundum Anglos (Anglo-Saxon week-days); secundum Scottos (days of the week ‘according to the Irish’). Each term begins with the word Diu, Classical Old Irish for dia, day. Diu, according to Ó Cróinín, “we have a clear reflex of the Indo-European nominative singular, with a lenghtened grade, giving arhaic Old Irish diu; it is suggested that what we have in the Oxford list and in Cormac’s Glossary is the oldest form of Old Irish dia, representing the old nominative case of the noun in adverbial usage.” (Ó Cróinín, 2003, p. 12).

The names in the Irish list are:

• dies scrol – Sunday. The word scrol is glossed in Sanas Cormaic as Scroll .i. soillsi, unde est aput Scottos diu srol .i. dies solis/Sroll, that is brightnexss, when ‘diu srol’ among the Irish, that is Sunday.

• Diu luna – Monday. Ó Cróinín has Diu luna as “represent[ing] the transitioal form between Latin dies lunae and the later, Classical Old Irish dia luain … a translation of, not a calque on, the Latin … [It] would seem to reflect a pre-assimilation state in respect of both words” (2003, p. 13), again demonstrating the antiquity of the forms. It is now rendered as Dia luain, Monday.

• Diu mart – Tuesday. “The Irish word perhaps derives from Latin forms where cases other than the genetive were used, e.g., Marte.” (2003, p. 15)

• Diu iath – Wednesday. A form unique to Irish, meaning uncertain. See following.

• Diu eathamon – Thursday. A form unique to Irish. Ó Cróinín writes “I suggest that it means simply ‘on Thursday’ … it is temporal dat. of an n-stem (nom. sg. etham, gen. sg. ethamon – as in our Oxford list – and acc./dat. sg. ethamain).” (2003, p. 17) He furthermore suggests that etham (‘arable land’) “may be a noun of agency from ith (gen. sg. etho), with a meaning like corn-maker or some such thing; Diu eathamon might then be a day for sowing seed in a weekly regimen of activities such as we find in Críth Gablach.” (2003, p. 17). A “very old” word for Wednesday, Mercúir (borrowed from the Latin (dies) Mercurii), does occur in early Leinster poems but Ó Cróinín is of the believe that Diu eathamon “reflects a still older Irish word for ‘Wednesday’;”.

• Diu triach – Friday. A form unique to Irish, its meaning unclear.

• Diu satur – Saturday. Error for Diu Saturn, because of omission of the n-stroke.

The form Ethomuin is found in Rawlinson B 502.

[edit] Germanic languages

The Germanic peoples adapted the system introduced by the Romans but glossed their indigenous gods over the Roman deities (with the exception of Saturday) in a process known as Interpretatio germanica. The date of the introduction of this system is not known exactly, but it must have happened later than AD 200 but before the introduction of Christianity during the 6th to 7th centuries, i.e. during the final phase or soon after the collapse of the Western Roman Empire. ^[2] This period is later than the Common Germanic stage, but still during the phase of undifferentiated West Germanic. The weekday names in Scandinavian languages were not calqued from Latin directly, but taken from the West Germanic names.

• Sunday: Old English Sunnandæg (pronounced [sun.nan.dæg] or [sun.nan.dæj), meaning "sun's day". This is a translation of the Latin phrase dies Solis. English, like most of the Germanic languages, preserves the original pagan/sun associations of the day. Many other European languages, including all of the Romance languages, have changed its name to the equivalent of "the Lord's day" (based on Ecclesiastical Latin dies Dominica). Compare: Spanish and Portuguese domingo, French dimanche, Romanian duminică, Italian domenica and Irish domhnach. In both West Germanic and North Germanic mythology the sun is personified as a goddess, Sunna/Sól.
• Monday: Old English Mōnandæg (pronounced [mon.nan.dæg] or [mon.nan.dæj'), meaning "moon's day". This is likely based on a translation of the Latin name dies lunae (cf. Romance language versions of the name, e.g., French lundi, Spanish lunes, Romanian luni, Italian lunedì, Irish luan). In North Germanic mythology, the moon is personified as a god, Máni.
• Tuesday: Old English Tīwesdæg (pronounced [ti.wes.dæg] or [ti.wes.dæj], meaning “Tiw’s day.” Tiw (Norse Týr) was a one-handed god associated with single combat and pledges in Norse mythology and also attested prominently in wider Germanic paganism. The name of the day is based on Latin dies Martis, “Day of Mars” (the Roman war god); compare: French mardi, Spanish martes, Romanian marţi, Italian martedì and Irish mairt.
• Wednesday: Old English Wōdnesdæg (pronounced [woːd.nes.dæg] or [woːd.nes.dæj) meaning the day of the Germanic god Wodan (later known as Óðinn among the North Germanic peoples), and a prominent god of the Anglo-Saxons (and other Germanic peoples) in England until about the seventh century. It is based on Latin dies Mercurii, "Day of Mercury"; compare: French mercredi, Spanish miércoles, Romanian miercuri and Italian mercoledì. The connection between Mercury and Odin is more strained than the other syncretic connections. The usual explanation is that both Wodan and Mercury were considered psychopomps, or leaders of souls, in their respective mythologies; both are also associated with poetic and musical inspiration. The Icelandic Miðviku, German Mittwoch and Finnish keskiviikko all mean 'mid-week'.
• Thursday: Old English Þūnresdæg (pronounced [θuːn.res.dæg] or [θuːn.res.dæj]), meaning the Þunor’s day. Þunor is commonly known in Modern English as Thor, the god of thunder in Germanic Paganism. Old High German’s name for Þunor, Donar, leads to Donnerstag. (The modern German word for “thunder” is still Donner.) The day is based on the Latin dies Iovis, “day of Jupiter”; compare: French jeudi, Spanish jueves, Romanian joi and Italian giovedì. In the Roman pantheon, Jupiter was the chief god, who seized and maintained his power on the basis of his thunderbolt (Fulmen).
• Friday: Old English Frīgedæg (pronounced [fri.je.dæg] or [fri.je.dæj]), meaning the day of the Anglo-Saxon goddess Fríge. The Norse name for the planet Venus was Friggjarstjarna, ‘Frigg‘s star’. It is based on the Latin dies Veneris, “Day of Venus“; compare: French vendredi, Spanish viernes, Romanian vineri and Italian venerdì. Venus was the Roman goddess of beauty, love and sex.
• Saturday: the only day of the week to retain its Roman origin in English, named after the Roman god Saturn associated with the Titan Cronus, father of Zeus and many Olympians. Its original Anglo-Saxon rendering was Sæturnesdæg (pronounced [sæ.tur.nes.dæg] or [sæ.tur.nes.dæj]). In Latin it was dies Saturni, “Day of Saturn”; compare French samedi. The Spanish and Portuguese sábado, the Romanian sâmbătă, and the Italian sabato come from Sabbata dies (Day of the Sabbath). The Scandinavian Lørdag/Lördag deviates signifficantly as it has no refference to the old norse gods, the latin gods nor the roman gods. It derives from old norse laugardagr, which literary translates to washing-day.

[edit] Indian astrology

The Greco-Roman scheme of planetary names was also adopted into Indian astrology during the 2nd century AD. Sanskrit attestations of the navagraha “nine astrological forces”, seven of which are used for day names, date to the Yavanajataka “Sayings of the Greeks”, a 150 AD translation of a 120 AD Greek Alexandrian text.

Though the explanation on the sequence of the name is only available in ancient texts in India. Which goes as below,

The division of days among the planets was done based on the speed of each planet as perceived from earth. Sun and Moon being the nearest and most important planets were allotted first two days and then the planet next in sequence to the original position of the planet was given the next day.. The sequence based on speed is Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn.

So after Sunday and Monday, the next to Sun was Mars hence the day was ‘Mangalwar’, next to moon was Mercury and hence ‘Budhawar’ next Mars was Jupiter and hence Guruwar , next to Mercury was Venus and hence ‘Shukrawar’ , next to Jupiter was Saturn and hence ‘Shaniwar’ and thus the seven names in this particular sequence.

[edit] East Asian Seven Luminaries

The East Asian naming system of week-days closely parallels that of the Latin system and is ordered after the “Seven Luminaries” (七曜), which consists of the Sun, Moon and the five planets visible to the naked eye. The five planets are named after the five elements in traditional East Asian philosophy: Fire (Mars), Water (Mercury), Wood (Jupiter), Metal (Venus), and Earth (Saturn). The earliest known reference in East Asia to the seven-day week in its current order and name is the writings attributed to the Chinese astrologer Fan Ning, who lived in the late 4th century of Jin Dynasty. Later diffusions from the Manichaeans are documented with the writings of the Chinese Buddhist monk Yi Jing and the Ceylonese Buddhist monk Bu Kong of the 8th century under the Tang Dynasty. The Chinese transliteration of the planetary system was soon brought to Japan by the Japanese monk Kobo Daishi; 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 era. In China, with the founding of the Republic of China in 1911, Monday through Saturday in China are now numbered one through six, with the reference to the Sun remaining for Sunday （星期日）.

Pronunciations for Old Chinese names are given in Modern Standard Chinese.

[edit] Numbered weekdays

[edit] Weekdays numbered from Sunday

For the majority of the Abrahamic religions the first day of the week is Sunday. Biblical Sabbath (originally corresponding to Saturday), when God rested from six-day Creation, made the day following Sabbath the first day of the week (corresponding to Sunday). Seventh-day Sabbaths were sanctified for celebration and rest. After the week was adopted in early Christian Europe, Sunday remained the first day of the week, but also gradually displaced Saturday as the day of celebration and rest, being considered the Lord’s Day.

Saint Martin of Dumio (c. 520–580), archbishop of Braga, decided it unworthy to call days by pagan gods and decided to use ecclesiastic terminology to designate them. This was the birth of the present Portuguese numbered system.^{[citation needed]} Martin also tried to replace the names of the planets, but was not successful. In the Middle Ages, Galician-Portuguese retained both systems. The Roman gods’ names are still used in Galician.

In the Hebrew and Islamic calendars the days extend from sunset to sunset. Thus, Jewish Shabbat starts at sunset on Friday and extends into Saturday nightfall when three stars become visible.^[3] The first day of the Islamic calendar, yaum al-ahad, starts on Saturday after sunset and extends to sunset on Sunday.

Icelandic is notably divergent, maintaining only the Sun and Moon (sunnudagur and mánudagur respectively), while dispensing with the names of the explicitly heathen gods in favour of a combination of numbered days and days whose names are linked to pious or domestic routine (föstudagur, “Fasting Day” and laugardagur, “Washing Day”). The “washing day” is also used in other North Germanic languages, although the Pagan names generally are retained.

[edit] Weekdays numbered from Monday

The ISO prescribes Monday as the first day of the week with ISO-8601 for software date formats.

The Slavic, Baltic and Uralic languages (except Finnish) adopted numbering but took Monday rather than Sunday as the “first day”.^[4]

Chinese Sunday means “week day” (星期日 or 星期天). Monday is named literally “first day of the (seven-day) week cycle”, Tuesday is “second day of the (seven-day) week cycle”, and so on. When China adopted the Western calendar Sunday was at the beginning of the calendar week but today Monday is preferred.

A second way to refer to weekdays is using the word zhou (周), meaning “cycle.” Therefore Sunday is referred to as zhoumo (周末), meaning “cycle’s end” and Monday through Saturday is termed accordingly zhouyi (周一) “first of cycle,” zhouer (周二) “second of cycle,” and etc.

Another Chinese numbering system, found in spoken Mandarin and in southern dialects/languages (i.e. Cantonese and Min), refers to Sunday as the “day of worship” (禮拜日 or 禮拜天) and numbers the other days “first [day after] worship” (Monday) through to “sixth [day after] worship” (Saturday). The Chinese word used for “worship” is associated with Christian and Muslim worship.

[edit] Weekdays numbered from Saturday

In Swahili the day begins at sunrise, rather than ending at sunset, and so offset by twelve hours from the Arabic and Hebrew calendar. Saturday is therefore the first day of the week, as it is the day which includes the first night of the week in Arabic. Etymologically speaking, Swahili has two fifth days of the week, although this is not widely recognized. The word for Wednesday, Jumatano, contains the number five in Swahili: tano. Tano is of Bantu origin. The word for Thursday, Alhamisi, is of Arabic origin and literally means the fifth (day). The word for Friday, Ijumaa, is also of Arabic and means (day of) gathering for the Friday noon prayers in Islam.

[edit] Mixing of numbering and planetary names

In Žejane dialect of Istro-Romanian, lur (Monday) and virer (Friday) follow the Latin convention, while utorek (Tuesday), sredu (Wednesday), and četrtok (Thursday) follow the Slavic convention.^[6]

There are several systems in the different Basque dialects.^[7]

[edit] Notes

[edit] Monday

^☽1 After No Work
^☽2 After Bazaar
^☽3 Head of Week
^☽4 Master (as in Pir, because Muhammad was born on a Monday^{[citation needed]})

[edit] Tuesday

^♂1 Thing (Assembly)
^♂2 Second day of the week (cf. Hungarian kettő “two”)

[edit] Wednesday

^☿1 Mid-week or Middle
^☿2 The First Fast (Christianity)
^☿1 Hump-Day

[edit] Thursday

^♃1 The day between two fasts (An Dé idir dhá aoin, contracted to An Déardaoin) (Christianity)
^♃2 Five (Arabic)

[edit] Friday

^♀1 The Fast (Celtic) or Fasting Day (Icelandic) (Christianity)
^♀2 Good Friday or Preparation (Christianity)
^♀3 Day of Faith (Islam)
^♀4 Gathering/Assembly/Meeting (Islam)

[edit] Saturday

^♄1 Shabbat or seventh-day Sabbath (Judeo–Christian)
^♄2 Wash or Bath day
^♄3 Sun-eve (Eve of Sunday)
^♄4 After the Gathering (Islam)
^♄5 End of the Week (Arabic Sabt = Rest) (Islam)
^♄6 Week
^♄7 Half good day holy day

[edit] Sunday

^☉1 From Latin dominicus “the Lord” (Christian Sabbath)
^☉2 Holy Day (Christianity)
^☉3 Resurrection (Christianity)
^☉4 Bazaar Day
^☉5 Market Day
^☉6 No Work
^☉7 Full good day