Masa Shivaratri, a meritorious Shiva Pujan, is observed on Chaturdashi in Krishna Paksha (Vad Paksh) of each Hindu month. It is also known as Monthly Shivaratri. Masa Shivaratri in March 2012 is Maha Shivaratri (20 February 2012). It falls in Falgun month in North Indian Hindi calendars and in Magha month as per the Panchangas followed in Andhra Pradesh, Karnataka, Gujarat & Maharashtra.
Pradosha Kaala is the best and meritorious period to worship Lord Shiva on Masa Shivaratri. Pradosh kaala time is between 4.30 to 6 PM.
Another most significant aspect of Masa Shivaratri in March 2012 (Maha Shivaratri) is – it falls on Somvar (Monday) which is the most favorite day for Lord Shiva.