This is the easiest door into the tradition that we know of, because you are already standing in it. You have used a seven-day week your whole life, and each day of it carries the name of a planet. Most people never notice, because English has hidden four of the seven behind Norse gods. Sanskrit hid none of them.
The seven, side by side
The Sanskrit word for a day of the week is vāra. Put the planet's name in front of it and you have the day. That is the entire system, and it is why the Sanskrit names are so transparent.
| English | Sanskrit | Planet | Deity of the day | The same planet in |
|---|---|---|---|---|
| SundayOld English sunnandæg, the Sun's dayToday | Ravivar रविवारRavi, the Sun | Sun | Suryathe Sun himself | English keeps it directlyFrench dimanche is the one day the Church renamed |
| MondayOld English mōnandæg, the Moon's dayToday | Somvar सोमवारSoma, the Moon | Moon | Shivawho wears the crescent Moon | English keeps it directlyFrench lundi, from Luna |
| TuesdayTiw, the Germanic war god, standing in for MarsToday | Mangalvar मंगलवारMangala, Mars | Mars | Hanumanstrength, protection | French mardi, MarsSpanish martes, Italian martedì |
| WednesdayWoden, standing in for MercuryToday | Budhvar बुधवारBudha, Mercury | Mercury | Ganeshain many households, Vishnu | French mercredi, MercurySpanish miércoles |
| ThursdayThor, standing in for JupiterToday | Guruvar गुरुवारGuru, Brihaspati, Jupiter | Jupiter | Vishnuand Brihaspati, the teacher of the gods | French jeudi, JoveSpanish jueves, Italian giovedì |
| FridayFrigg, standing in for VenusToday | Shukravar शुक्रवारShukra, Venus | Venus | Lakshmiprosperity; also Durga | French vendredi, VenusSpanish viernes, Italian venerdì |
| SaturdayOld English Sæternesdæg, Saturn's dayToday | Shanivar शनिवारShani, Saturn | Saturn | Shaniand Hanuman, for shelter from him | English keeps it directlyFrench samedi went to the Sabbath instead |
Read the two outer columns together and the pattern closes. English kept the Sun, the Moon and Saturn under their own names. French kept Mars, Mercury, Jupiter and Venus under theirs. Between the two languages every one of the seven planets is still visible, and every one of them matches the Sanskrit.
Monday. Somvar. Lundi. Three languages, one Moon.
Why the days are in that order
Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn is not the order of the planets in the sky, nor their order by brightness, nor by distance. It is the result of a piece of arithmetic that both the Roman world and the Indian one inherited, and it is worth seeing once, because after that the week never looks arbitrary again.
The ancient astronomers ranked the seven visible planets by how slowly they appear to move against the stars, slowest first: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. Then they gave each hour of the day to a planet, going down that list and starting again at the bottom. Whichever planet rules the first hour rules the day.
So the planet that rules the first hour of the next day is always three steps further down the list. Start Saturday with Saturn. Count three on: Sun. Three more: Moon. Then Mars, Mercury, Jupiter, Venus, and back to Saturn. That is the week.
The Sanskrit word for one of those planetary hours is horā. It is the same word as the Greek hōra, and it is the same word as the English hour. The three languages are not merely describing the same thing. They are using the same word for it.
The seven-day planetary week is not in the Vedas. The Vedic calendar counted by the Moon's nakshatras and by the lunar month. The planetary week reached India in the early centuries of the common era, through the same Hellenistic astronomy that gave it to Rome, and the Sanskrit texts that carry it, beginning with the Yavanajātaka, say so in their own name: yavana means Greek.
That is not a weakness of the correspondence. It is the reason for it. The week went east and west from a common source, and both ends kept it. The Indian tradition then did something the West did not: it assigned each day a deity and a practice, and has kept that practice alive, unbroken, ever since.
What a day is for
In a Hindu household the day of the week is not neutral. Each one belongs to a deity, and observant people give that day a shape: a fast, a visit to a particular temple, a colour to wear, an offering to make. The practice is called vrat, a vow, and it is the most ordinary form of devotion there is. Nobody needs a priest for it.
Monday belongs to Shiva, and the Monday fast, Somvar vrat, is among the most widely kept in India. Tuesday and Saturday are Hanuman's, and the queues at Hanuman temples on those two days are a fixture of every town. Thursday is for Vishnu and for the guru; it is the day students and seekers traditionally honour their teachers. Friday is Lakshmi's, the day of prosperity, and the day a shopkeeper cleans the shrine at the front of the shop. Saturday is Shani's, Saturn's, the planet of delay and discipline, and it is approached with more caution than the others: sesame oil, a black cloth, a visit rather than a request. Sunday is the Sun's, and Wednesday is Ganesha's, the clearer of obstacles, which is why new ventures tend to begin on it.
None of this is required of anyone. It is a rhythm, and the point of a rhythm is that it is there whether or not you keep step.
Why it matters for a ceremony
Every Yagya we commission is timed. The priests choose the day, and often the hour, for the deity being addressed and the purpose being served, using the practice called muhurta. The day of the week is one of the inputs, alongside the Moon's nakshatra and the lunar date. A ceremony to Lakshmi sits naturally on a Friday. One for strength or protection sits on a Tuesday. One that has to begin something sits on a Wednesday, or in the Abhijit hour around midday.
Which means that when a recording reaches you, the day it was performed on was chosen, and the choice can be read. This page is the first half of learning to read it. The twenty-seven nakshatras are the second.