Today, 6 December 2012 is Bhairavnath Jayanti, Mahakaal Bhairav Jayanti or Kalashtami. It is the first appearance day of Lord Kalabhairav. It falls on Krishna Paksha Ashtami in Margashirsha Month. Mahakaal Bhairav, Bhairavnath or Kaalbhairon is a manifestation of Lord Shiva who appeared to punish Lord Brahma.
As per the Shiva Maha Purana, headstrong Brahma ordered Vishnu to worship as he was the creator of the universe. Angered Shiva appeared in the form of Kalabhairava and cut down the fifth head of Brahma. Since then, Brahma has only four heads.
Kalabhairava Temple in Varanasi (Uttar Pradesh) & Kal Bhairav Temple in Ujjain (Madhya Pradesh) are the most popular temples in India dedicated to Bhairavnathji.
Mahakaal Jayanti is celebrated with utmost gaiety in Tamil Nadu, Rajasthan, Madhya Pradesh, Uttar Pradesh and Nepal.