In Indian calendrical systems,vāra (or,vāsara) denotes theweek-day. It is one of the five elements that constitute the traditional almanacs calledPañcāṅga-s the other four beingNakshatra,Tithi,Karaṇa andNityayoga.^[1] The concept of week, the unit of time consisting of seven days, is not indigenous to Indian civilisation. The concept was probably borrowed byBabylonians and its use predates the use of the twelve zodiacal signs in Indian civilazation. The concept finds mention inAtharva Veda. The seven week-days are named after the seven classical planets as in the ancient Greek and Roman traditions.^[1][2][3]

The historical rationale behind the current naming of the week-days is astrological in origin and it can be summarized as given below.Surya-Siddhānta andĀryabhaṭīya have also indicated this rationale.Sūrya Siddhānta, in Chapter XIIBhūgolādhyāya Verses 78–79, says:^[2]

"The Lords of the days are to reckoned in order fourth from Saturn downwards. The Lords of the hours are also to be reckoned commencing from Saturn downwards."

Explanation of the rationale

Assume that the classical ancient planets be revolving round the earth. The planets are arranged in the order from slowest to fastest moving as they appear in the night sky, or equivalently, in the order from furthest to nearest to earth. The planets in this order are Saturn, Jupiter, Mars, Sun, Venus, Mercury and Moon. It is further assumed that a day is divided into 24 equal parts orhora-s. The planets are assigned to the 24hora-s in the same order as indicated earlier one by one cyclically. On a given day, the cycle of planets will be repeated three times. The planet assigned to the firsthora on a given day would be the planet immediately following the planet that was assigned to the 24thhora of the previous day. The name of the week-day on a given day will be the name associated with the planet associated with the firsthora of the day. Thus, if the planet associated with the first hora of a day is Sun, the planet associated with the next day would be Moon, the planet associated with the third day would be Mars, and so on. The order of the weekdays thus becomes Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn.

This rationale is reflected in one of the literal meanings of the Sanskrit wordvāsara (another term forvāra) which is "relating to or appearing in the morning".^[4]

The rationale behind the naming of the days of a week is certainly not of Indian origin. Also the concept of a seven-day week as a unit of time is not of Indian origin. The system of dividing a day into 24hora-s is there in India only in the astrological literature. Works on astronomy likeSurya-Siddhānta andĀryabhaṭīya do not mentionhora as unit of time. In such works, the common practice is to divide day into 60ghaṭi-s and eachghaṭi into 60vighaṭi-s. Moreover, no work of the Vedic and the Vedāṅga period mentions it. Further, the wordhora is not even of Sanskrit origin. Chaldeans had this unit in use since a long time and they did have a week of seven-days.Vāra-s were known to Chaldeans long before 3800 BCE. It is probably the case that the ancient Indian astronomers and astrologers borrowed the concept ofvāra or week from the Chaldeans.^[2]

TheAtharva Veda contains references tovāra. From evidences obtained fromAtharva Jyotiṣa andYājñavalkya Smṛti, it has been determined that thevāra-s began to be used in a period much earlier than the period when the 12 zodiacal signs began to be used. Thus, in the Indian subcontinent, the use ofvara-s predates the use of therāśi-s. The days of the week may have been introduced in India at about 1000 BCE and they are not more modern than 500 BCE.^[1][3]

The names of thevāra-s in all of the 22 languages recognized by theConstitution of India^[5] are given in the following table. For a longer list, see:Week-days in languages of the Indian subcontinent.

• Nakshatra
• Tithi
• Karaṇa
• Nityayoga
• Planetary hours

• Calendars
• Units of time
• Hindu astronomy
• Astronomy in India
• History of astronomy

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