Mahashivaratri is essentially a religious festival unlike Onam and Thiruvathira. The word means `the great night of Shiva`.
According to the Sivapurana, it falls on Krishna Chaturdasi day, which is the fourteenth day during the waning of the moon in the month of Megha, though in some years it may occur in Phalguna also. In Kerala, the month of Kumbh is noted for the Shivaratri festival, which falls in February-March.
The festival is said to commemorate the day on which Shiva protected the world from a total annihilation either by drinking the deadly Kaalakooda poison, which was held up in his neck, or by effecting a healthy compromise between Brahma, the Creator and Vishnu, the Protector.
Mahashivaratri is considered a very important day for fasting and Shiva worship.
In many respects, the Shivaratri festival in Kerala can be considered a miniature Ardha Kumbh Mela that is held at Triveni, the confluence of the holy rivers Ganga-Yamuna, and the invisible Saraswati. The Annual Shivaratri Festival held on the banks of Periyar at Alwaye is one of the most spectacular local festivals of Kerala that attracts thousands of pilgrims from all over the State.