Pradosham means an auspicious evening time (an hour and a half before and after sunset) dedicated to worship Lord Shiva and his mount Lord Nandi. Pradosham evening is celebrated especially on the 13th tithi (trayodashi) of the waxing and waning lunar cycle.
The legend goes like this: Once Lord Indra while riding on his mount “Airavata” (celestial white elephant) came across Sage Durvasa on the way, who offered him a special garland as a blessing. Indra took it and kept it on the head of his Airavata. The flowers had a strong scent which attracted bees, annoyed by the bees, the Airavata threw the garland on the ground. Looking at this gesture, the angered Sage cursed Indra and the rest of the devas to be bereft of their power, pride, fortune and everything from their disposal. Soon they were defeated by the asuras in a battle led by King Bali.
Indra lost everything and finally went to Lord Vishnu, who told him that churning the celestial ocean (ocean of milk) is the only way to retrieve all that was lost. The diplomatic Indra convinced the asuras to jointly churn the celestial ocean for the nectar of immortality (Amrita). They used the mount “Mandara” as the churning rod and the snake “Vasuki” from the neck of Lord Shiva as the rope. Asuras took the side of the snake's mouth and devas took the side of the tail. The churning went on full swing but then the mount Mandara began to sink. Watching this, Lord Vishnu took the avatar of Lord Kurma (form of turtle) to support the mountain on his shell so that they could churn continuously.
Due to continuous twists and pulls, the snake Vasuki started emitting poison fumes from its mouth (known as Halahala or Algol). The poison was so intense that they all ran away from the ocean towards Lord Shiva, who then swallowed the poison and saved all of them. Lord Shiva further performed a Tandava (cosmic dance) in between the horns of his mount “Nandi” to make them happy. Everyone witnessed Shiva's Tandava including Vishnu, Brahma and all the celestial sages. This moment of great blessings of Shiva is called “Pradosham”.
Five types of Pradosham
Nitya Pradosham (daily)
Paksha Pradosham (fortnight)
Maasa Pradosham (monthly)
Maha Pradosham (yearly)
Nitya Pradosham: It comes every evening roughly an hour and a half before and after sunset (around 4.30 pm to 7.30pm if we take 6pm as the average sunset time).
Paksha Pradosham: It comes on the 13th tithi (trayodashi) of the waxing lunar cycle.
Monthly Pradosham: It comes on the 13th tithi (trayodashi) of the waning lunar cycle.
Maha Pradosham: Trayodashi tithi comes on a Saturday is called Maha Pradosham aka Great Pradosham. It got its name due to the reason that the above said legend occurred on a Saturday.
Pralaya Pradosham: Pralaya means “end”. In vedic puranas the term Pralaya is used to denote the ending of the final age when all living beings will look towards Lord Shiva to save them. This time is called Pralaya Pradosham.
Pooja vidhi (method of prayer): Take bath in the morning at sunrise time then worship Lord Nandi and Shiva by chanting the mantra for 108 times. Start the fast (vrat) from then on and keep it till sunset (Pradosham time). Perform Shiva and Nandi pooja in the evening by pouring milk (abhishekam) over Shivlingam and Nandi while chanting the mantra. Devotees also offer honey, sandalwood paste, curd, vibhuti (ash), Indian bael, rice, fruits etc. But milk is considered as the most important ingredient as it denotes pure love. Then light an incense and chant the mantra for 108 times once again. End the fast after pooja by eating something.
Mantra: You can chant the "Nandi Gayatri Mantra" or "Maha Mrityunjaya Mantra" or "Om Namah Shivaya".