The Supreme Lord said:
I instructed this imperishable yoga to Vivashvaan.
Vivashvaan taught it to Manu.
Manu spoke it to Ikshvaaku.

This verse continues from the previous. Knowledge, inaccesible from the lust-covered heart, is given by Krishna to the Sun-god, who passes it one through his sons. Thus wisdom becomes disseminated throughout the world's leaders, who in turn pass it to their followers.

The second half of the verse introduces a problem: over the vast expanse of time, the original knowledge sometimes scatters and is lost as it is passed from one person to the next. Krishna will give the solution to this problem in the next text

We can estimate from this verse the age of the knowledge contained within Bhagavad Gita. Krishna says that he spoke imam yogam (this knowledge) to Vivashvaan, who then educated his son in the same knowledge. This means that Krishna must have educated Vivashvaan before the education of Vivashvaan's son. Vedic literature estimates that the age of Vivashvaan's son is approximately 120,000,000 solar years. Thus the knowledge contained within Bhagavad Gita is at least 120,000,000 years old.

As will be clear from the next text, the current form of Bhagavad Gita was spoken to Arjun just before the Battle of Kurukshetra, which Vedic Historians and astronomers calculate as roughly 5,000 years in the past.

Understanding the antiquity of Gita may help us better appreciate the weight of the knowledge it contains.