Vrindavan where there is no past and future, rather only the present in which the Lord relishes transcendental loving pastimes with all his associates; but in this material world the Lord performs occasional pastimes called Naimittika-Leela, such taking birth and killing the demons. One such Naimittika-Leela that he performed in his pastimes in Bhauma Vrindavan was on the ashtami tithi in the month Kartik, when the Lord took the calfs for the first time for grazing at a very young age, and on the same day after a few years he took out the cows for grazing. Therefore this festival is celebrated as Gopashtami.
The Supreme Personality of Godhead, Shri Krishna, also celebrated as Govinda, the one who gives pleasure to the cows, and Gopal, the one who takes care of the cows, ever engages Himself in herding, milking and taking care of the Surabhi cows in the most magnificent holy land of Vrindavan, filled with lush green grass, tender and delicious, which is relished by the cows, at the banks of the river Yamuna, the crystal clear and fragrant waters of whose currents are sweeter than nectar and are enjoyed by the cows of Vrajendranandan Shyamsundar.
Sukadeva Gosvami said: Thus the Vrindavana forest was filled with transparent autumnal waters and cooled by breezes perfumed with the fragrance of lotus flowers growing in the clear lakes. The infallible Lord, accompanied by His cows and cowherd boyfriends, entered that Vrindavana forest.'
Nanda Maharaj is the father of Lord Sri Krishna. Those days children were given the charge to take care of the calves. Both Lord Krishna and Balarama having passed their fifth year, cowherd men conferred and agreed to give those boys who had passed their fifth year charge of the cows in the pasturing ground. Nanda Maharaj decided to organise a ceremony for Lord Krishna and Balarama while going for cow grazing for the first time in Vrindavan. Radha, Lord Krishna's divine consort, wanted to graze cows but was denied of being a girl. So, she disguised herself in a boy because of her resemblance to Subala-sakha, She put on his dhoti and garments and joined Lord Krishna for cow herding along with her companions for funs. The festival is celebrated on the eighth day in the bright half of Karthik month