Origin of weekday names

I had published it as an appendix (Appendix A) in my book ‘The Historic Rama’.

It is reproduced here, on my blog, per requests of many, for wider circulation.

Appendix A



Sudarshan Bharadwaj & Nilesh Nilkanth Oak

The nomenclature of the weekdays is similar across multiple cultures. The weekdays in many European languages are named after the Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn, respectively.
For example, the weekdays in English are: Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, and Saturday. Of these, Sunday, Monday, and Saturday are readily recognizable as being named after the Sun, Moon, and Saturn, respectively. Tuesday is derived from “Tiv’s day,” which is named after the Norse god of single combat, Tyr. Wednesday is derived from “Woden’s day,” Thursday from “Thor’s day,” and Friday from “Freya’s day.” Among the Norse gods and goddesses, Tyr is identified with Mars, Woden with Mercury, Thor with Jupiter, and Freya with Venus. This nomenclature is also similar to that in Northern European languages such as Danish, Dutch, or Swedish. Similarly, the weekdays in French, Italian, and Spanish are named, for the most part, after the Roman days of the Sun, Moon, Mars, and so on to Saturn.
European sources attribute the nomenclature of the weekdays to the Greeks or the Babylonians. However, there is scant evidence for these claims, and the claims are mostly based on conjectures, circular logic and uninformed opinions.
We will look at four sets of explanations, two ancient Indian texts on astronomy and two from individual scientists/researchers from last two centuries.

Aryabhatiya & Surya Siddhanta

Both are well known, most referred and most esteemed. Like many Indian classical works, they are poems in the Sanskrit language.
Not trivial works by any means, they cover cosmology, planetary motions, eclipses, conjunctions, star positions, risings/settings, mathematics, geography, instrumentation and model-making. Both of them are not conventional textbooks in the sense that they are too succinct and somewhat cryptic for a rank beginner. They are rather meant as a concise aid to instruction for the experienced teacher.
While both works share commonalities, Surya Siddhanta is much older. Aryabhatiya appears to be from fifth century CE. In his excellent work, Anil Narayanan (see selected bibliography) has shown that while Surya Siddhanta has been updated several times (last update as recently as 580 CE), possibly the actual epoch was as far back as 7300 BCE- 7800 BCE, in antiquity.


To date, the best explanation for this particular ordering of the weekdays and their association with various grahas comes from a verse in the Aryabhatiya, composed by the Indian mathematician and astronomer Aryabhatta (Aryabhatiya, KalaKriya Pada, Verse, 16):

सप्तैते होरेशा: शनैश्चराद्या यथाक्रमं शीघ्रा:|
शीघ्रक्रमाच्च्तुर्था भवन्ति सूर्योदयाद् दिनपा: ||

The (above mentioned – mentioned in previous verse) seven Grahas beginning with Saturn, which are arranged in the order of increasing velocity, are the lords of the successive hours. The Grahas occurring fourth in the order of increasing velocity are the lords of the successive days, which are reckoned from Sunrise (in Lanka).

(Sanskrit word ‘Graha’ is generally translated as ‘planets’ in astronomical context. This is a mistake. The meaning of ‘graha’ is ‘one that grasps’. Thus, in the astronomical context, the word ‘graha’ means an astral object that grasps another astral object (e.g. ‘Graha’ approach-ing a nakshatra – a visual delusion, of course). It also means an astral body that exerts attractive force on the earth.)
What we have above is a ‘mnemonic device’. The original form or explanation can be understood or explained in few different ways.
The lords of the twentyfour hours (with hours being measured from sunrise at Lanka) are: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter, Mars, respectively, and the lords of the seven days are: Saturn, Sun, Moon, Mars, Mercury, Jupiter, Venus, respectively.
The lord of the day is the lord of  the first hour of that day, the day being measured from sunrise.

Surya Siddhanta

Surya Siddhanta has similar explanation (Bhugoladhyaya -78)

मन्दादध: क्रमेण स्युश्चतुर्था दिवसाधिप:
होरेशा सूर्यतनयादधोध: क्रमशस्तथा
Starting from the Saturn downward, the fourth graha is called the lord of the day. The graha starting from the Saturn successively downwards are the lords of the hour.

Another way to understand this explanation is shown in the table:

Sudarshan picture

Shri Suhas Gurjar of Jyotrividya Parisamshta-Pune made one of the authors aware of this Aryabhatiya reference. He also provided an explanation. It is summarized in the table below: Shri Gurjar has made it intuitive by using 6 AM as a proxy for the sunrise. Weekday is named after the ‘graha’ corresponding to 6 AM of that day, beginning with Shani (Saturn) and thus Saturday.

Suhas Gurjar picture

Sudarshan Bharadwaj did exhaustive search for the origins of weekday names. He found that as of November 2013, there are no other rational explanations for the order of weekdays (i.e. other than Aryabhatiya) anywhere in the world. Of course there is no dearth of explanations however they share a common theme. All of these remaining explanations are convoluted and circular in nature, claiming the origin, arbitrarily, to Babylonians or Greeks, based on opinions, conjectures and speculations however with characteristic lack of factual evidence.

The only rational explanation for the nomenclature of the weekdays comes from an Indian source. No other culture provides any reason for why a particular graha (planet) is associated with a particular day of the week. Only the Indian Jyotish (Hora-shastra) provides the rationale, and not some folklore reason, but rather an astronomical one.
Hindu concept of seven day week is much older and has other associated astronomical issues. In Judaism, seven day week is taken for granted without any introspection. There is no development of ideas or background on the issue, which indicates that this concept was borrowed, ready-made, from another culture. Judaism is not the only culture to do so. Other cultures have also done this. All of them have seven day week. And none of them have any associated astronomy with it to decide why it should be seven days and which day corresponds to which planet (or deity) and rationale for the sequence.
We are asserting that ancient cultures of Europe/Africa/Arabia (Greece, Rome, Egypt, Babylonia, etc.) were not aware of the true rationale behind naming and sequence of week days. We are asserting that western civilization to this day is not aware of the true rationale behind naming and sequence of week days. These assertions are based on the evidence as of November 2013. Of course, we are not denying the possibility of discoveries of old manuscripts among above mentioned cultures that refers to ancient Indian explanation for the naming of weekdays.
One of the authors searched the internet and Wikipedia, exhaustively, for any and all references in this context. We also saved screenshots of these Wikipedia searches (as of November 2013). Reader must be aware that information on Wikipedia is dynamic and while Wikipedia is a decent source of information for numerous noncontroversial subjects; when it comes to subjects of critical importance (philosophy, original research, appropriation and digestion of ideas) Wikipedia is, as Rajiv Malhotra puts it, “a sinister force behind the deceptive mask of fairness and level playing field.”   Readers may visit http://www.rajivmalhotra.com to know more about original and groundbreaking work of Rajiv Malhotra.

Sir Oliver Lodge (1893 CE)

And before someone jumps and claims that Europe was aware of this true rationale by the time of Copernicus, Kepler, Galileo and Newton; let me refer them to the explanation offered by Sir Oliver Lodge (Pioneers of Science, Macmillan & Co, 1893, pages 17-19).
Lodge states that seven grahas were known: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn and states that they were supposedly ordered in this sequence due to their distance from the earth. He also mentions that at times the sun was thought to be nearer than Mercury or Venus. He states that Mars, Jupiter and Saturn were placed in that order because that is the order of their apparent motions, and it was natural to suppose that the slowest moving bodies were furthest off.
The explanation for the sequence of days (beginning with Sunday) is similar to one offered by Aryabhatta, however without the comprehension of its true rationale. It is not clear if Lodge is referring to the order of grahas round the circle counterclockwise, as the method of astrologers of his day, or his own way of explaining it. The method works, however, I want to emphasize that Lodge has not shown awareness of the underlying rationale and explanation of Aryabhatta.
And while on the subject I want to make another observation. Lodge states that science of Greek was remarkable, at least in some areas. However he laments that it largely based on what has proved to be a wrong method of procedure, viz. the introspective and conjectur-al, rather than the inductive and experimental (I suppose the correct method in Lodge’s opinion) (emphasis mine).
Unfortunately, both Greeks and Lodge missed the correct method, although each of them shared an element of it, viz. conjectural and experimental.
He summarizes the procedure for weekday names using the following diagram.

Sir Lodge picture

Dr. P V Vartak

Available ancient Indian literature is vast, in spite of the fact that much has been lost. No wonder likes of Dr. P V Vartak, who has done much original research and much of it based on astronomy observations, still missed either Surya Siddhanta or Aryabhatiya references for the rationale of weekday names.
In his words (A Realistic Approach to the Valmiki Ramayana, Blue Bird, 2008, pages 302-306),

The Sun was held as atman and the Moon was held as the manas, the first name given to the weekday from the Sun, e.g. Aditya. The next day was named after the Moon, e.g. Soma. Then they (sages) gave alternate names, once from the Moon and once from the Sun. This means they selected grahas alternately from the external and the internal group. After Monday, they took Mangal (Mars) from the external group, then Budha (Mercury) from the internal, then Guru (Jupiter) from external, then Shukra (Venus) from internal, then Shani (Saturn) from the external.

The point I want to make is that if we have an existing order, one can always retrofit an explanation that may be arbitrary and still logical. This could be then a proposal of European astrologers, Sir Oliver Lodge or Dr. P V Vartak.

Division of Day in 24 Parts

Nilesh Oak did exhaustive search for the origins of division of the day into 24 hours and found that online references to be full of conjectures and speculations, but little evidence.
Internet search produced the following that is worth mentioning:
Our 24-hour day comes from the ancient Egyptians who divided day-time into 10 hours they measured with devices such as shadow clocks, and added a twilight hour at the beginning and another one at the end of the daytime. Nighttime was divided in 12 hours, based on the observations of stars. The Egyptians had a system of 36 star groups called ‘decans’ — chosen so that on any night one decan rose 40 minutes after the previous one. In the Egyptian system, the length of the ‘daytime’ and ‘nighttime’ hours were unequal and varied with the seasons. In summer, daytime hours were longer than nighttime hours while in winter the hour lengths were the other around.
We were aware of multiple time measurement systems in Indian astronomy but could not think of any system that divided the day into 24 parts. This is crucial for explanation of ‘mnemonic devices’ provided by Aryabhatiya and Surya Siddhanta. While both of them provided measurement system of time, the division of the day into 24 parts was not suggested. Ancient Indian literature does present multiple time measurement systems and existence of a system that divided a day into 24 parts is intuitive for a civilization that has Luni-solar calendar, 12 months, six seasons, etc. That is all fine. But did we have document-ed evidence of such?
Srimad Bhagavad Purana, Skandha 3, Adhyaya 11, Shlok 1-14 provided one such evidence. It presents time measurement system as follows:
1 Ahoratra (day & night) = 8 Prahar = 24 hours
1 Aha= 1 ratra = 4 Prahar = 12 hours
6 or (7) Nadika (Danda) = 1 Prahar = 3 hours
2 Nadika (danda) = 1 Muhurta = 60 minutes
15 Laghu = 1 Nadika = 30 minutes
15 Kashtha = 1 Laghu = 2 minutes (120 Sec-onds)
5 Kshana = 1 Kashtha = 8 seconds
3 Nimesh = 1 Kshana = 1.6 seconds
3 lav = 1 Nimesh = 0.53 seconds
3 Vedha = 1 lav = 0.17 seconds
100 Truti = 1 Vedha = 0.056 seconds
3 Trasarenu = 1 Truti = 0.00056 seconds
3 Anu = 1 Trasarenu = 0.00019 seconds
2 Paramanu = 1 Anu = 0.000063 seconds
1 Paramanu = 0.000032 seconds

We want to make few observations:

1. While we were aware of ancient Indian time measurement system where: ‘1 AhoRatra (24 hour day) = 30 Muhurtas’ and thus ‘1 Muhutra = 48 minutes’, the above time measure-ment system from Srimad Bhagavad Purana refers to ‘1 Muhurta = 60 minutes = 1 hour = 1 hora’.
2. This is then not unlike the difference between US and UK Gallon: same unit of measurement (Muhurta) with different magnitude (60 min vs. 48 min). Three significantly different sizes are in current use: Imperial gallon (~4.546 L), US gallon (~3.79 L) and US Dry gallon (~4.40 L).
3. The fact that 6 or 7 Nadika corresponds to 1 Prahar, also means 24-28 Nadika corresponded to 1 Aha (daylight). This flexibility appears to be result of changing length of the day (and night) between 12-14 hours, with changes in the season. Flexibility in the length of daytime (sunlight) is useful for civic purposes (not unlike ‘daylight saving time’ adjustments).
4. The system of dividing a day into 24 parts called ‘hora’ seems to be relevant only in consideration with the theory of week days and astrology. Otherwise astronomy works seem to employ different time units.
5. Above observations point to the fact that this system of time measurement described in Srimad Bhagavad Purana was suitable for both astronomy and astrology purposes, for the astronomy timekeeping and also for the civic timekeeping.
6. Varahamihira has suggested Sanskrit origin of ‘hora’ by explaining that the word is ‘coined’ by taking the middle portion of the word ‘ahoratra’, leaving out ‘a’ and ‘tra’.


3 thoughts on “Origin of weekday names

  1. The two time measures in general use were Ghatika, 60 ghatikas making one day or ahoratra and each ghatika being made up of 60 palas. Since when they came in use is not known to me. Even in my own childhood I remember having seen a Ghatika-patra an exact measure of ghatika like an hour -glass. Time used to be designated as x ghatikays and y palas from sunrise. Do you find the timing of any event in an epic or literature or any other grantha mentioned as ‘so many horas from sunrise or sunset’? hora was probably a part of time-keeping by the civil society.

  2. Were seven days a part of south american civilizations? What is the position about China? What about old cultures in African tribes? From India to Rome, all had close contacts and internal exchange of knowledge and ideas so a week with 7 days is a common feature.

  3. As far as I recollect, there is no mention of name of the day (वार) anywhere in Mahabharata. Day was recognizes by the titish and by the nakshatra in which moon was seen. Shortest measure of group of days was paksha, normally 14 or 15 days. Concept of week was not in vogue. Where earliest is the concept of a week of 7 days is mentioned as in use, in old Indian literature or religious texts? A 7 days’ week keeps no relation with Lunar Paksha or month or lunar/solar year. Wherefrom this unit of time period came in use? And for what purpose? After Aryabhata?

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