How old is the Gita?
Like Ved, the Gita is eternal and is reproduced on the earth planet at regular intervals. When Shree Krishn told the Gita to Arjun 5,000 years ago, it was not the first time it was told. In the beginning of the fourth chapter, Shree Krishn tells Arjun that He had revealed the same knowledge to the sun god Vivaswat before the beginning of the current manvantar (a period of time corresponding to one hour in Brahma's day; there are 14 manvantar in one day of Brahma - we are currently in the seventh). Before that, there were many other times as well, because Shree Krishn tells the same Gita every time He descends on earth.
The Gita is part of the extensive and fully coordinated system of Sanskrit scriptures that forms the basis of Sanatan Dharm, the eternal and universal religion for all the souls. The word 'sanatan' means eternal, and 'dharm' means those thoughts, words and actions that foster good qualities in a person, and ultimately take him to God. So, if Sanatan Dharm is eternal, then it means the knowledge of Sanatan Dharm is eternal. That knowledge remains in the form of the Ved, Upnishad, Gita and other Hindu scriptures, which reside eternally within God in their Divine form and are maintained here on the earth planet in a book form. It is all a part of the process of srishti: the manifesting and maintenance of the creation which gives a chance for the souls to realize God.
God Reveals the Knowledge of Sanatan Dharm
The souls are eternal and have been seeking God since eternity, but they cannot know about God on their own because God is beyond human intellect. The only way would be for God to make Himself known to the souls, and He does - through the Vedas, Gita and other Hindu scriptures that He produces on the earth planet. Thus, in the eternal cycle of creation and dissolution of the universe, the souls have been taking birth after birth since eternity, and in every birth, the knowledge of God and of dharm has been available through these scriptures.
Mantaining the Availability of the Hindu Scriptures on the Earth Planet
In order to maintain the availability of these scriptures for the guidance of the souls, sometimes the books have to be reproduced. There is a system for this as well. All of these scriptures are reproduced at the end of every dwaparyug by a descension of God called Ved Vyas (each manvantar is divided into 71 cycles of the four yugas; each cycle corresponds to one minute of Brahma's day - we are currently in the 28th cycle of the seventh manvantar - thus, we are currently in the 28th dwaparyug of this manvantar). This means that Ved Vyas has reproduced the scriptures 28 times in this manvantar alone. When he comes, Ved Vyas re-writes all the Hindu scriptures, including the Ved, Darshan Shastras, Puranas, Ramayan, and the Mahabharat, which includes the Gita. The latest such reproduction was 5,000 years ago.
In the next part, I will address the question of whether the conversation recorded by Ved Vyas in the Gita is a word-for-word transcript of the conversation between Krishn and Arjun, or if it was somehow expanded upon at a later date.
Note: The entire Bhagavad Gita series by Swami Nikhilanand will continue, once or twice a week, for more than a year and will be an incredible study aid in learning the deepest aspects of Bhagavad Gita from one of the most profound and prolific speakers of Bhagavad Gita in the English speaking world today.