Shiva rathri is one of the most auspicious day for the devotees of Lord shiva
Every month in Krishna paksha chathurdhasi (fourteenth moonday) is called masa Shiva rathri. The one that comes in the month of "Masi" (mid February to mid March) is called Maha Shiva rathri. This is considered as the most important day by the devotees.
Worship of Lord Shiva continues all through the night on Shivaratri Festival. Devotees stay awake all night and spend the night in Shiva temples in worship of Lord Shiva. Singing of hymns and verses in praise and devotion of Lord Shiva besides the intense chanting ofOm Namah Shivay,the mantra that is said free people from all their sins, continue through the night on Shivaratri.