On the occasion of Maha Shivratri millions of Shiva devotees keep a fast all day and pray through the night. The festival, which falls on March 4 this year, is one of the holiest days in the Hindu calendar and the most important among the 12 Shivratris celebrated throughout the year. Some say this was the day when Shiva manifested himself in the form of a linga, and the Puranas mention that Shiva wed Parvati on this day. But why do Hindus celebrate this birthday or even the marriage, which was as tempestuous and interesting as most human marriages?