Why do we celebrate Mahashivaratri?

Amongst many stories that portray why we celebrate Mahashivaratri, here are four main reasons why is Shivratri celebrated:

1. Mahashivaratri marks overcoming darkness and ignorance in life by worshipping Shiva. The Lord is honored by chanting mantras, fasting and contemplating ethics and virtues of divine life.
2. It is said that on the day of the absolute formless God Sadashiv appeared in the form of “Lingodbhavamurti” during the midnight. 180 days after Shivratri, Vishnu appeared as Lord Krishna at Gokul in midnight. That event is celebrated as Janmashtami. Thus, the entire year is divided into two by both these auspicious days of the Hindu Calendar.
3. Shivratri is also celebrated as Lord Shiva and Devi Parvati’s wedding anniversary. It is said that without Parvati Shiva is pure ‘Nirguna Brahman’; with Parvati, he becomes the “Saguna Brahman.”
4. It is believed that on Shivaratri Lord Shiva gulped poison that arose during the churning of “Kshir Sagar.” The poison was so deadly that if its single drop fell into Shiva’s stomach, it would have poisoned the entire world. To safeguard the world, he held it in His neck, which turned blue. This is how Shiva came to be known as Neelkanth.