Masa Shivaratri, or Mas Shivratri, falls on the Krishna Paksha Chaturdasi of each traditional Hindu lunar month. Below are the dates of Shivratri in 2011. ‘Krishna Paksha’ is the dark fortnight of a lunar month. It is the 13th day after full moon (Purnima) or more easy calculation one or two days before Amavasi. Shiva devotees observe the day with vrat, special prayers and pujas. Some devotees also keep vigil all night as in Mahashivratri.
Other important myths include that of Taandava, the consummation of poison during the churning of ocean, hunter accidentally dropping the leaves of bilva, the loss of importance of ketki flower, which is now only offered during shivaratri.
Shivratri is celebrated a night before ‘amavasya’ (full dark night) in the month of Magh or phalgun (February – March). The significance of Shivaratri is closely associated with ‘amavasya.’ Amavasya represents Kaliyuga. Lord Shiva appeared just before the beginning of Kaliyuga to rid the world of evil and ignorance, which is symbolically represented through Amavasya. Therefore Mahashivratri is celebrated to get rid of evil and ignorance.
On the Shivratri day, Lord Shiva is worshiped in a special form of Linga called ‘Lingodabhavamurti or Jyotirlinga.’ It is a lingam in the form of fire which has neither a beginning nor an end. It must be noted here that ‘linga’ only means ‘sign.’ And it is merely an attempt to capture the formless.
Apart from this there are numerous legends and myths associated with Shivratri. An important myth is that Shivaratri is the birthday of Lord Shiva – this is mainly because the formless Lord Shiva appeared for the first time in the form of ‘Lingodabhavamurti’ before Lord Vishnu and Brahma.