The question from the saintly persons—there were many questions—one of the question was that, "After departure of Kṛṣṇa, who is in trust of dharma and jñāna?" Dharma means religion, and jñāna means knowledge. Because Kṛṣṇa, when He appeared on this planet, He said that:
- paritrāṇāya sādhūnāṁ
- vināśāya ca duṣkṛtām
- dharma-saṁsthāpanārthāya
- sambhavāmi yuge yuge
- (BG 4.8)
"I appear in every millennium." According to Vedic scripture, Kṛṣṇa appears on this planet in one day of Brahmā. And Brahmā's duration of life is described in the Bhagavad-gītā. It is a very, very long period. His one day, daytime, twelve hours, from morning to evening, is described, sahasra-yuga-paryantam arhad yad brahmaṇo viduḥ (BG 8.17). Sahasra-yuga. Yuga, this age. Just like this is, according to Vedic culture, this yuga is called Kali-yuga.
So there are four yugas: Satya-yuga, Tretā-yuga, Dvāpara-yuga and Kali-yuga. So the aggregate of all these yugas is about forty-three hundred thousands of years. And if you multiply by one thousand, then that becomes Brahmā's one day only, twelve hours. Sahasra-yuga-paryantam arhad yad brahmaṇo viduḥ. So similarly, he has got one night also, and similarly, one day and night, then one month, then one year. In this way he lives for one hundred years. So during this period of daytime, Kṛṣṇa appears once. That we learn from the Vedic literature.