Age of the Earth and ancient knowledge according to H.P.B.

According to the mainstream science and radiometric age dating, Earth is about 4,54 billion years old. Now this isn't yet a big shaker except perhaps to the modern day creationists (Wikipedia).

Something that I found surprising, is how ancient people could've know all this with such precision, as mentioned in Mahâ-Kalpa, which is supposed to be an ancient Hindu (or Indian in general, I am not sure whom has invented this theory) astronomical period of time measurement. (Wikipedia).

Russian occultist, Helena Blavatsky, mentioned these notions in her book 'Isis Unveiled', published in 1877. She concluded - based on above information revealed on Mahâ-Kalpa - that age of the Earth is around 4,3 billion years.

Based on the above, the ancient science almost ridicules our modern day science, which widely believed, is the most sophisticated system of acquiring information and only achievement of recent times. Well, someone before 'our science' had pretty accurate knowledge about the suspected age of the Earth.

I'm just starting to comprehend the value of Blavatsky's book, since I've merely read about 200 pages of it. From what I've read, it is fairly interesting book and there are other interesting thoughts in it. Allow me to freely translate from my localized version:

"The Greek called this year by the name of 'heliakos', but no-one outside the inner circle did not know anything certain about their exact lenght nor other details [...] Commentators has been very uncertain about the length of this period that no-one has been able to figure out the truth, except Herakleitos who considered it to be 10.800 year long, and Linus whom thought it to be 13.984 years old." (Isis Unveiled)

Well, I am sure I've heard that kind of figures somewhere before. I hope someone can contribute on this thread in a constructive manner.

Sincerely,