In Hinduism, each day of a week is dedicated to a particular god in the Hindu pantheon. Apart from the special Vratas* and Upvaas (fasting), many Hindus also fast on a particular day in a week. Each day in a week has a specialty and there are numerous folklores associated with the fasting observed on the days of a week.
Sunday is dedicated to Lord Surya (Sun God). Those who undertake fast (upvaas) on the day only take a single meal. Oil and salt is avoided. Red is the color of the day and red flowers are offered to Surya.
Monday is dedicated to Lord Shiva. It is said that Lord Shiva is easily pleased. Therefore many people observe Upvaas on Monday. Those devotees observing fast only eat food once. People visit Lord Shiva shrines and conduct pujas, especially, Ardhanarishwara puja. The mantra ‘Om Namah Shivaya’ is chanted continuously. Siva devotees also read Shiva Purana. Unmarried women observe the Vrat to get good husbands. Others observe it for a happy and prosperous family life.
Tuesday is dedicated to Lord Ganesha, Durga, Goddess Kali and Lord Hanuman. Most devotees visit Devi and Hanuman shrines. Those people who fast avoid taking food containing salt at night.
Wednesday is dedicated to planet Mercury and Lord Vithal, an incarnation of Krishna. Green color leaves, especially Tulsi leaves, are used in Pujas. The day is highly auspicious for starting new ventures and it is believed that those who observe the Vrat are bound to get blessed with fortunes. People also give alms on the day.
Thursday is dedicated to Lord Vishnu and his incarnations. Pujas are conducted using milk, ghee etc. Food is only eaten once and that too containing milk products. People read Srimad Bhagavad Purana on the day.
Friday is dedicated to Mother Goddess – Mahalakshmi, Santhosi Ma, Annapuraneshwari and Durga. Sweets are distributed on the day. Those devotees observing the Vrat make it a point to eat at night.
Saturday is dedicated to alleviating the bad influence of Lord Shani. The Vrat on this day is mainly observed by those people who believe in Hindu astrology. Black is the color of the day and people visit Shani shrine or Navagraha shrines. Food is only consumed once on the day.
It must be noted here that the deity worshipped on a particular day might vary from region to region and community to community. The result of all upvaas or fast depends on the person. It is good, if all the members in the family can undertake a Vrata together.
Miracles do happen by observing a particular Vrata and the greatest miracle is Brahman realization. All rituals and observances are path towards understanding the Supreme Soul and this will automatically alleviate all sufferings.
* Vrata is a Sanskrit word that means "vow, resolve, devotion", and refers to pious observances such as fasting and pilgrimage (Tirtha) found in Indian religions such as Jainism and Hinduism.