During the month of Sawan, Devotees worships Lord Shiva's form Bhairava, but it is performed on the day of Kalaashtami. It is said that Kalaashtami is celebrated every month of the Krishna side. Devotees worship the Bhairav form of Lord Shiva and fasts on this day. This fast is considered to be very fruitful. On the other hand, worshipping Kaal Bhairav by fasting on this day removes all sufferings and in this fast, Bhairavnath should be worshipped with hexadecimal treatment and he should dedicate Arghya.
At the same time, on this day, one should wake up at night and listen to the story of Lord Shiva and Mata Parvati and listen to the Bhairav Katha. It is said that on this day, at midnight, the shankh, nagada, bell should be played and Lord Bhairav's aarti should be served to his vehicle, Swan, to please Him. On the other hand, fasting should be accepted and it is said that this fast is considered to be very fruitful.
At the same time, the One who fasts Kalaashtami avoids all the hassles and it may be beneficial to chant the whole day of the fasting one: Kalbhairmaya Namak. On the other hand, it is said that following this fast with a pure mind will help in every task.