Mahashivaratri is one of the important Hindu festivals, celebrated with pomp and gaiety. It is celebrated on 13th or the 14th night of the new moon during Krishna Paksha in the Hindu month of Phalgun (equivalent to the Maasi month in Tamil Calender), which corresponds to February-March in Gregorian calendar. The festival is celebrated on moonless night. This year it is fall on 12th February 2010 (equivalent to 31st day of Thai month in Tamil Calender in stead of the Maasi month).
The festival is dedicated to Lord Shiva, Mahashivratri honors the goodness and power of the Almighty. Since Lord Shiva is one among the Hindu Trinity (the other two being Lord Brahma and Lord Vishnu), he is worshipped by almost everyone, who has faith in Hinduism (Vaishnavas being the exception). Lord Shiva is known for his short-temper, which is often brought down by the pacifying effect of his significant half - Goddess Parvati.