If you make an estimate of the time, then that estimation also, we can make from Vedic literature. That estimation is . . . I have made an estimation. It is about four hundred millions of years before, it was spoken. So far, as far as we get the information of Bhagavad-gītā from Mahābhārata, we understand that this Bhagavad-gītā was spoken to Arjuna about five thousand years before.
But we have to calculate in the Fourth Chapter that the Lord says that, "I spoke to the sun-god, and sun-god spoke it to Manu, and Manu spoke to Ikṣvāku." And the next verse He says, evaṁ paramparā-prāptam imaṁ rājarṣayo viduḥ (BG 4.2): "So this confidential knowledge of Bhagavad-gītā was received in such disciplic succession." Disciplic succession. Just like the Lord Kṛṣṇa said to the sun-god, and the sun-god said to Manu, and Manu said to Ikṣvāku, and He summarizes that evaṁ paramparā-prāptam: "In such disciplic succession, the knowledge of Bhagavad-gītā was received."
Sa kāleneha mahatā yogo naṣṭaḥ parantapa. Now, He says that "This yoga . . . " This Bhagavad-gītā is also called yoga. Karma-yoga, jñāna-yoga, bhakti-yoga. You'll find in Bhagavad-gītā different yogas. So the whole book is called yoga. Now, here also it is stated, sa kāleneha mahatā yogo naṣṭaḥ parantapa: "My dear Arjuna, oh, you are the great hero. Now, that Bhagavad-gītā, the instruction which I imparted to the sun-god, was coming by disciplic succession, now it is lost."
Now, we have to note down this point. Why it is lost? Why it is lost? Do you think that there was no learned man during that time? During Kṛṣṇa's time? Oh, there are many learned sages. Not only one, two; there are dozens of learned sages. But still, the Lord says, Kṛṣṇa says, that "They . . . that knowledge which I exactly imparted to sun-god is now lost." How it is lost? There were many scholars, and still, how it is lost? The lost means that the purport of Bhagavad-gītā is lost.
Because scholars, they can interpret in their own way about Bhagavad-gītā, but that is not Bhagavad-gītā. That is not Bhagavad-gītā. That is the purpose which Kṛṣṇa wants to stress. So any student of Bhagavad-gītā must note it, that Bhagavad-gītā commented by a person—he may be very scholar in the material sense, but that scholarship will not help to comment on the Bhagavad-gītā.
The Bhagavad-gītā, to understand Bhagavad-gītā, we have to accept this disciplic succession principle as Lord Kṛṣṇa says to Arjuna that, "It is coming down by disciplic succession." We have to take that spirit. And without taking that spirit, simply by our erudite scholarship if we want to understand Bhagavad-gītā, that is a misunderstanding. That is the purpose He has said.
Now, He also again clears the subject matter. Sa evāyaṁ mayā te 'dya yogaḥ proktaḥ purātanaḥ (BG 4.3): "So Arjuna, I am just trying to speak to you about that old system of Bhagavad-gītā yoga, old system of yoga which I first spoke to sun-god." "Why? Why You are speaking to me?" The question . . . "You say that the spirit of Bhagavad-gītā is lost, and You are . . . why You have selected me to speak the Bhagavad-gītā?
There are many learned men. There is Vyāsadeva. There is Vasiṣṭha. There is other, many sages. They are existing. I am an ordinary military man. I am a family man. I know simply fighting. So why You are anxious to speak to me about Bhagavad-gītā? Why You are anxious to speak to Me? I am not a Vedāntist. I am ordinary man. So why?"
Now, the reply is bhakto 'si. Just see. Bhakto 'si me sakhā ceti rahasyaṁ hy etad uttamam; "O My dear Arjuna, I am just trying to speak to you Bhagavad-gītā because you have got an exceptional qualification which others haven't got." And what is that exceptional qualification? Here it is clearly mentioned, bhakto 'si. Bhakto 'si. Bhakto 'si means "You are My devotee. You know that I am the Supreme Personality of Godhead, and therefore you have surrendered yourself unto Me, accepted Me, Myself, as the spiritual master. You know. You are My devotee."