So the Kṛṣṇa consciousness movement is so nice that it makes a person perfect in everything: perfect in knowledge, perfect in strength, perfect in age, everything. We need so many things. So this perfection of life, the process how to make life perfect, is coming down from Kṛṣṇa. Kṛṣṇa, He is the origin of everything. Therefore the knowledge of perfection is also coming from Him, and periodically-periodically means after millions and millions of years—Kṛṣṇa comes. He comes once in a day of Brahmā. So Brahmā's days, even one day, the span of one day, it is very difficult to calculate. Sahasra-yuga-paryantam arhad yad brāhmaṇo viduḥ (BG 8.17). The Brahmā's one day means about 433,000,000's of years. So in each day of Brahmā, Kṛṣṇa comes, once in a day. That means after a period of 433,000,000's of years He comes. Why? To give perfect knowledge of life, how a human being should live to make his life perfect. So the Bhagavad-gītā is there, spoken by Kṛṣṇa in this millennium, in this day. Now Brahmā's one day we are passing through the twenty-eighth millennium. No, twenty-eighth... In Brahmā's day there are seventy-one Manus, and one Manu lives for... That is also many millions of years, seventy-two millenniums.
So we are not interested now about calculation the perfect knowledge. This perfect knowledge comes from God, or Kṛṣṇa, and it is distributed by paramparā system, by disciplic succession. The example is just there, a mango tree. On the top of the mango tree there is a very ripened fruit, and that fruit has to be tasted. So if I drop the fruit from up, it will be lost. Therefore it is handed over, after one, after one, after... Then it comes down. So all Vedic process of knowledge is taking from the authority. And it comes down through disciplic succession. Just like I have already explained, Kṛṣṇa gives the knowledge, perfect knowledge, to Brahmā, and Brahmā gives the knowledge to Nārada. Nārada gives the knowledge to Vyāsa. Vyāsa gives the knowledge to Madhvācārya. Madhvācārya gives the knowledge to his disciplic succession, later on, to Mādhavendra Purī. Mādhavendra Purī gives that knowledge to Īśvara Purī. Īśvara Purī gives that knowledge to Caitanya Mahāprabhu, Lord Caitanya. He delivers that knowledge to His immediate disciples, six Gosvāmīs. The six Gosvāmīs delivers the knowledge to Śrīnivāsa Ācārya, Jīva Gosvāmī. Then Kavirāja Gosvāmī, then Viśvanātha Cakravartī, then Jagannātha dāsa Bābājī, then Bhaktivinoda Ṭhākura, then Gaura Kiśora dāsa Bābājī Mahārāja, then my spiritual master, Bhaktisiddhānta Sarasvatī. Then we are distributing the same knowledge.