Why are there seven days in a week and not any other random number? Did you have this question when you were a child?
This sequence is based on the ancient Indian science of the stars known as Jyotish Shastra (astrology), described as the eyes of the Veda Purusha. It has its roots in our ancient knowledge of the workings of the planets - astronomy.
The order of the days in a week is defined according to the speed of the planets/astral bodies with reference to the movement of the Earth. There is a close relationship between the Earth and these planets, recognized a long time ago by Vedic astrology. But, of course, they also knew that only those planets close to us can affect us. Therefore, in the counting of the days of the week, only those grahas (planets) were taken whose vibration/light is within the range that affects the Earth. If we were living on another planet or another solar system, the number of weekdays and the duration of a day would be quite different from what we know today! This was stated in ancient Indian texts that the seven days of the week are based on the Earth’s relationship with its seven closest neighbors! The order is determined with reference to the movement of the Earth. The moon is the fastest, and Saturn is the slowest.
Of course, as usual, all Indian scientific knowledge was not recognized by Western historians who attributed the origin of this concept of the days of the week to the Sumerians, Babylonians, Greeks, and Egyptians—anyone but the Indians—all of whom date back to 2100 BCE at the most. The Indian texts like the Suryasiddhanta, said to be taught to Mayasura by Lord Surya (sun god) himself, the Pulastsaya Samhita, Parashara Samhita, and Hora Shastra can all be traced back to 3000 BCE.
We also have a host of other astronomers closer to the Christian era like Aryabhata, Varahamihira, Madhavacharya, Bhaskaracharya, etc. Indian astronomers knew about heliocentricity (the sun is the center of our system) long before Kepler’s theory of heliocentricity (1617-1621).
However, while calculating the order of the days, we have to follow the geocentric method. This is because we live on this planet, Earth, and if we follow the heliocentric method, we will have our first day as “earth-day” instead of “Sun-day,” and “moon day” or “Monday” will get omitted!
As per Vedic astrology, we have nine planets. So why is it that we have only seven days in the week? The reason for this is that Rahu and Ketu are considered to be lunar modes and not real planets.
“Hora” (from which the word “hour” comes) is a Sanskrit word derived from another Sanskrit word called ahoratra, which means “a complete day.” One ahoratra has 60 ghatis, which is equal to 24 horas, corresponding to nearly 24 hours. So, we can see how closely our present arrangements of hours and days correspond to the ancient Indian model.
To get the sequence of weekdays, our astronomers arranged the planets from slowest to fastest (according to their speed of rotation). The order comes out to be Saturn (Shani), Jupiter (Brihaspati, guru), Mars (Mangal), Sun (Ravi), Venus (Shukra), Mercury (Buddha), and Moon (Soma).
The first thing our astrologers did was to make a list of hours from 1 to 24 in a row. After that, they assigned one hora or hour to one graha or planet starting with Saturn, which was the slowest, followed by Jupiter, Mars, and so on as mentioned above in the order of their velocity in rotation. When you proceed like this, we will get to the 24th hour or hora in which we will get Mars or Mangal.
We then go to the next row and follow this very sequence starting with the 1st hour up to the 24th hour. This has to be done seven times so that we get 7 rows in which the 1st hour of each row is represented by the Lord of that day (dinapati). Therefore, the first row will have Saturn/Shani as its 1st hour, and the Sun or Ravi as the first in the second row. In the 3rd row, the first hour will have the Moon/Soma. In the 4th row, the first hour will be presided by Mars/Mangal. In the 5th row, the first hour will be Mercury/Buddha. In the 6th row, the first hour will be presided over by Jupiter/Brihaspati (Guru). In the 7th row, we will get Venus/Shukra in the first hour. Thus, we see that when we arrange these in a sequence, we will get the days of our week starting with Saturday (Shanivaar), Sunday (Ravivar), Monday (Somavar), Tuesday (Mangalvar), Wednesday (Budhhavar), Thursday (Guruvaar), and Friday (Shukravaar). These planets are considered to be the Lords (dinapatis) of these days.
Of course, now we follow the western calendar in which Sunday is the first day of the week for purely arbitrary reasons!
Another strange fact that our astrologers told us is that people work better on those days in which that particular planet dominates their birth chart. Another interesting fact is that these planets have certain colors. To live in greater harmony with the essence of the planets and strengthen them in your chart, one is advised to wear the colors they represent. Of course, there is no hard and fast rule about this, but you could follow this if you have an important interview or examination! They also have their specific gems and metals as well as gods.
Sunday
The Sun’s colors are red, gold, and orange.
Gem - Ruby
Metal – gold
God – Surya, sun god.
Mantra – Surya Gayatri
Monday
The Moon’s colors are white and pale pink, pale blue, watery-green, and all pastel shades.
Gem – Pearl
Metal – Silver
God – Shiva.
Mantra – Aum Namashivaaya
Tuesday
The colors of Mars are red, coral, and jet black.
Gem – Red coral
Metal – Iron
God – Hanuman; Durga
Mantra – Hanuman chalisa; Aum Durgaayai Namaha!
Wednesday
Mercury’s colors are emerald green, blues, grays, and browns.
Gem – Emerald
Metal – Quick silver or Mercury
God – Ganesha
Mantra – Aum Gam Ganapataye Namaha!
Thursday
Jupiter’s colors are yellow, orange, and gold.
Gem – Yellow sapphire
Metal – Tin
God – Guru; Krishna
Mantra – Aum Sri Gurubhyoh Namaha! Aum Namo Bhagavate Vaasudevaaya!
Friday
Venus has all the rainbow colors.
Gem – Diamond
Metal – Copper
God – Lakshmi, Saraswati (All benign forms of the divine mother)
Mantra: Aum Shrim, Hrim, Mahalakshmyai Namaha! Aum Aim Saraswatyai Namaha!
Saturday
Saturn has dark blue and black.
Gem – Blue sapphire
Metal – Lead
God – Saturn
Mantra – Aum Sham Shaneeswaraaya
Of course, all these details are only given to us to show what a lot the Vedic rishis knew about the planets and their workings. It might be impossible to follow all these things but perhaps for a special occasion or an exam or interview, we might use the colors and gems for the day for special benefits.
Another interesting fact is that these planets and therefore their days have specific functions. Certain days lend themselves to positive results so here we can give a list of these positive planets which are good for travel or for auspicious occasions like marriages, naming the ceremony of a child, and so on.
Mercury is the most benign of all the planets and hence Wednesday is generally considered good for all auspicious events and also for travel etc. Sundays, Fridays, Mondays, and Thursdays are also good. But of course, there are certain times in each day that are auspicious and inauspicious but it's best not to go into such detail.
Ganesha is the god to be propitiated before starting a journey or any other auspicious event. His day happens to be Wednesday. So, breaking a coconut to Ganesha before the start of a journey or an auspicious event will ensure that all obstacles on your path are removed.
The main thing we have to learn from this is to realize that the planets have a great influence on our lives. We should learn to respect them and understand this relationship in order to live a life of harmony with the cosmos. Only then will we become fulfilled individuals. That is why you find that all Hindu festivals are connected with some planet and especially the moon which is the closest to us.
Hari Aum Tat Sat!