On the day of Deepavali, something very special happens — our Lord declares, “Aham Govardhano’smi” (“I am Govardhana”), and He Himself transforms into the Govardhana Hill that stands in Brindavan.
As that very hill, He receives all kinds of offerings — various delicious dishes and foods — which the residents of Brindavan lovingly present to the hill. The Lord, in the form of the hill, Himself partakes of and enjoys all those offerings.
The next day, Indra becomes upset. He feels offended that no offerings or worship were made to him, and that no food was offered to him. That feeling of hurt soon turns into anger, and in his fury, Indra begins to pour down heavy rain — a storm of hail and thunder

From the very next day, it rains continuously for seven days. The downpour begins on the day after Deepavali.
As soon as the rain starts, Perumal (Lord Krishna) lifts the Govardhana Hill itself and holds it aloft like an umbrella. All the people of the village — the cowherds, the Gopikas, the elders, the cows, and the calves — all take shelter beneath that hill.

The Lord continues to hold up the mountain for seven days, protecting all the people beneath it.
Seeing this, Indra becomes frightened. On the eighth day — after the Lord places the hill back down — Indra comes and falls at the divine feet of the Lord, seeking forgiveness.
The people of Brindavan say with gratitude, “You protected all of us for so many days!” The cows, calves, and oxen all approach the Lord’s holy feet to take refuge in Him.

At that very moment, the celestial cows of the heavenly world — Surabhi and Nandini, the most exalted divine cows — also come before the Lord and perform Tirumanjanam (holy bathing) and Abhishekam to Him with their own milk.
The legend for that day is this — it is believed that on that day, the cows themselves perform worship to the Lord. Usually, it is Krishna who performs Go Pūjā (worship of cows). But on that day, the cows, feeling grateful that Krishna had protected them all through that great calamity, wish to worship Him in return.Since the cows cannot perform a full pūjā by themselves, we do it on their behalf.

                                                                                                                                                                                                   When should it be done? — On the seventh day from the day of Deepavali. That means, this month, it falls on the 29th. On that evening, the cows are to be beautifully decorated — adorned with ornaments, tied with colourful cloth, and their horns painted — just like we do for Mattu Pongal. After decorating them nicely, in the goshala (cow shelter), a small idol of Lord Krishna is to be ceremoniously placed (ezhundharulal).                                                                                                 The milk freshly taken from those cows should then be poured at the divine feet of that Krishna idol — everyone should participate in this offering. While doing so, each person should chant the name of Govinda at least 24 times.

        It may be chanted like this:

“      Govindā Hari Govindā Gokula Nandana Govindā.”

       Even this alone is sufficient.Each person should chant the Govinda nāma 24 times, then circumambulate (pradakṣiṇā) around the cows, and also around Perumal and Krishna. After that, milk payasam or milk sakkarai pongal (sweet pongal made with milk and sugar) should be prepared and offered (naivedyam) to the Lord. Then, that same prasadam should be given to the cows as well, and also distributed to the devotees.

      The most important part is — performing abhishekam to the Lord’s holy feet with milk, offering naivedyam of prasadam and fruits to the Lord, and doing archanai with flowers. Along with this, performing pradakṣiṇam (circumambulation) around both the Lord and the cows is very significant.

         If possible, one should make the effort to perform two pradakṣhiṇas — together with a cow and her calf — around the Lord.

        This is the pooja we should perform on that day — we do it on behalf of the cows, as their representatives, offering worship to the Lord. It is a very special form of worship.

         It is said that by performing this pūjā, the cows experience great joy. Even if one were to worship the cows directly, it would not give them as much happiness as when we — their representatives — offer worship to Krishna, remembering how He protected them on that day long ago.

        Because of this, the cows bless us abundantly — granting us wealth (dhanam), grains (dhānyam), happiness (sukham), joy (ānandam), prosperity, and position. Such is the greatness of this day — Gopāṣṭamī.

      It is an extremely special and sacred day. After the pūjā, people celebrate beautifully with traditional folk arts — kummi, kolāttam, and other dances — all performed as a joyful pradakṣiṇā around Lord Krishna, singing His divine names with devotion.

        Gopāṣṭamī is indeed a very auspicious day — this year, it falls on 29th October. On that day, let us all join together and celebrate it wonderfully!