One of the festivals that fall in the auspicious month of Kartika is Gopashtami. It is on this day that Maharaja Nanda put Krishna and Balarama in charge of cows, bulls, and oxen. Prior to this thinking Them too small, Nanda Maharaja had asked Them to tend the calves. Now, when they had come to the age of Pauganda (6 -10 years), Nanda Maharaja thought it proper to hand over the responsibility of herding cows to Them.
It is stated in the Kārttika-māhātmya section of the Padma Purāṇa:
śuklāṣṭamī kārttike tu
smṛtā gopāṣṭamī budhaiḥ
tad-dinād vāsudevo ’bhūd
gopaḥ pūrvaṁ tu vatsapaḥ
“The eighth lunar day of the bright fortnight of the month of Kārttika is known by authorities as Gopāṣṭamī. From that day, Lord Vāsudeva served as a cowherd, whereas previously He had tended the calves.”
Krishna thus began His Go Charana Lila wandering the forests bare feet herding cows and blessing the land of Vraja. The Gopis, however, felt profoundly anxious thinking of thorns and pebbles pricking His lotus feet soft as petals and some of them fainted considering the prospect.
It is also said that Krishna lifted Govardhana during the first seven days of the month of Kartika. On the eighth day, Lord Indra came to his senses and offered profuse apologies and prayers to Lord Krishna. He performed abhishekam of the Lord and a Surabhi cow bathed the Lord with her milk. From then on the Lord got the name Govinda – giver of pleasure to the cows. Gopashtami is also a celebration of this eight day of the Govardhana Lila.
Gopashtami is observed throughout Vraja with much fanfare involving the worship of cows, calves and Lord Krishna.