Shiva Purana says:
“He who worships Shiva during the holy Period of Pradosha,
With the offering of lotus flowers and a total surrender,
Will be blessed with longevity, devout wife, loving children and friends,
And will enjoy lots of prosperity and fortune in this world”.
Every month in the evening of trayodasi -13th moon phase between 4.30 p.m to 6p.m is Pradosham. It is observed in the twilight period – one and half hours before sunset and one hour after sunset.
It falls twice in a month,once in the waxing period or Shukla paksha and once in the waning period or Krishna paksha.
Pradosham hours are holy hours to wash away the sins of innumerable lifetimes. When one prays to the Lord with wholehearted devotion, the Lord wipes away the sins and fulfills all desires.
Pradosha Purana – Story of Neelkanth
Churning of Ksheerasagar
According to Shiva purana, on the holy day of dwadasi, the devas and asuras churned the milky ocean,Ksheerasagar, to attain the elixir of immortality. Lord Vishnu as a tortoise-kurma avatar, held the mandara mountain on his back to prevent it from falling into the ocean and serpent king, Vasuki was used to churn the mountain. The devas and asuras in their sheer excitement to consume the nectar( elixir), forgot to seek the blessings of Lord Shiva before churning the ocean.
Vasuki`s Spewing of Hala-Hala
While churning, the serpent, Vasuki , was subject to severe and intense strangulation, that it spewed poison or deadly venom called Hala-Hala. The venom caused great panic and distress among the devas. Lord Indra and other Gods sought the refuge of Lord Shiva in Mount Kailash. Lord Shiva was merciful to their pleadings. He sent Nandi, his vehicle to collect the deadly venom and bring it to him.
Drinking of Hala-Hala
Nandi brought the venom by collecting it from the ocean, as directed by the Lord, to Mt.Kailash. Shiva took the poison and drank it. Goddess Parvati knowing the danger of the effects of the deadly poison, rushed to Shiva and by her supreme powers forcefully stopped the flow of poison by gently placing her hands at the throat of Shiva. The hala-hala stopped at the throat of Shiva and his throat became blue in color. Thus, Lord Shiva got the name, “Neelkanth”-Blue Throated One
Poisonous Effects of Hala-Hala
The poison started taking its toll. Lord Shiva`s eyes rolled and closed, his feet stumbled rhythmically,breathing heavily,he beckoned Parvati and said to her,” Oh Gauri, don’t panic.To protect the devas,I had to drink this poison. The Hala-Hala is no ordinary poison. It’s effect is deadly and devastating. It will have its same effect on me and my creations…. I must rest… May I lay on your lap, Oh divine mother?”
Shiva`s Deep Rest
The devas, rishis watched the Divine Mother sit down and place the Lord`s head on her lap. Shiva`s throat was blue hued and the Lord was seen with eyes closed.The whole of Kailasha was in deep silence. The devas gathered around the Lord and prayed to him to revive.One and half days passed by and in the evening of trayodasi on a Saturday, the Lord showed signs of movement. The Lord woke up slowly and placed his arm around Parvati and mercifully glanced at the Devas.
Shiva`s Sandhya Tandava
Much to everyone`s surprise for the next one and a half hours from 4.30 p.m to 6 p.m, Lord Shiva performed the divine dance between Nandi`s two horns. It is the twilight period, presided by Pratyusha, another wife of Surya. It is called Pratyushat Kaal. Later it became Pradosha Kaal.
This celestial dance of Shiva was performed on Nandi`s head, between the two horns to drive away the ego possesed by Nandi. Nandi became inflated with pride when he came to know that he remained unaffected by the poison, while the Lord of the universe had to undergo the deadly effects.
Nandi felt inflated and danced with pride. To heal Nandi of wrong thoughts, by his supreme grace, he danced with his lotus feet and enlightened Nandi.