In Hinduism, Mahashivaratri (also called Shiva Ratri) is the great festival of Lord Shiva. It is held on the 14th day of the dark half of the lunar month of Phalguna. Mahashivaratri is especially important to Saivites (devotees of Lord Shiva), but it is celebrated by most Hindus.
The day of Mahashivaratri is spent in meditation on Lord Shiva and fasting (some may take water or fruit). Temples dedicated to Lord Shiva are filled with devotees offering prayers. The Shiva lingaat in the temple or in one's home is bathed with milk, honey and water, and offerings are made to Lord Shiva in the form of Bilva leaves, fruits and other specially prepared foods. Offering Bilva leaves to Lord Shiva on Mahashivaratri is considered especially auspicious.
Devotees sing hymns and chant mantras, especially Om Namah Shivaya. Some sit around a sacred fire and toss offerings of grain into the flames while chanting to Lord Shiva. After fasting and meditating throughout the day, a vigil is held all night with continued prayers and meditation.
Various legends are associated with Mahashivaratri. One is the popular legend of the ‘Churning of the Ocean of Milk’, in which the gods inadvertantly unearthed a poison that threatened to destroy the world. Lord Shiva saved the day by drinking the poison, which accounts for his blue throat in some Hindu art.
It is said that Lord Shiva was strong enough to handle the poison, but he had to stay awake all night as part of his healing. The other gods helped get him through the night by entertaining him with dances and other distractions. This is commemorated on Mahashivaratri, when Lord Shiva's followers keep him company through the night.
Another legend tells the story of a hunter who climbed a Bilva tree to escape a hungry lion. The lion sat down beneath the tree and waited for the hunter to fall. As he waited on the tree all night, the hunter plucked leaves from the Bilva tree to stay awake.
The leaves, which are sacred to Lord Shiva, fell on a Shiva linga that happened to be at the base of the tree. Lord Shiva was pleased with the offering, inadvertant though it was, and saved the hunter. This event is commemorated on Mahashivaratri by staying up all night and offering Bilva leaves.