Kalashtami is observed on the eighth day during the waning
phase of moon (Krishna Paksha Ashtami) in a lunar month as per traditional
Hindu lunar calendar. The day is dedicated to the Kala Bhairav form of Shiva. Here
are the rules that should be followed while performing or observing Kalashtami
Vrat.
Apart from the Kalbhairav form of Shiva, the Ishana form of
Shiva is also worshipped on the day.
The pujas and rituals begin at midnight when there is
Ashtami Tithi. An arati is performed first at midnight to Kalbhairav.
People observing the vrat should keep all night vigil.
Prayers dedicated to Kalbhairav are chanted on the night. Prayers and puja end
just before sunrise.
The vehicle of Kalbhairav is a black dog. Food is offered to
black dog on the day.
The importance of Kalashtami Vrat is mentioned in the Aditya
Puran.
There is also a popular belief that during the afternoon
period of Krishna Paksha Ashtami Tithi, Bhairavnath, an important Shiva Gan,
was also born.