September 16, 2017: Indira Ekadasi
September 17, 2017: Vyatipata Mahalayam, Kanya Sankranthi, Pradosha Vratam
September 18, 2017: Kaliyugadi, Gajachhaya Parvam, Vishasastrahata Mahalayam, Maasa Sivarati
Bhairava is fearsome manifestation of Lord Shiva. Bhairava Ashtami is a holi festival day earmarking the birth of Bhairava. It falls in Krishna Paksha, on the 8th day of the Hindu month of Margshirsh.
Dog is the carrier (vehicle) of Lord Bhairava. Hence dogs are worshipped on this day.
The general custom is to remain fast and taking water to conclude the vrat. Praying to Lord Shiva and Goddess Parvathi are done.
An argument as to who is the most powerful came up between Lord Brahma and Lord Vishnu. Sages are called up to decide upon the matter. Shiva was unhappy at the attitude and argument of Lord Brahma and transformed into a Bhairava (Dog). Bhairava chops the fifth head of Lord Brahma and hence will be left with four heads. Because of fear at what has happened, everyone begins to offer prayers to Bhairava / Lord Shiva.