The one of the early mentions of Yuga theory of Satya, Treta, Dwapara and Kali occurs in Manu Smriti.
There the Yuga is acutally only 12000 years with
- Kali Yuga - 1200 years
- Dwapara Yuga - 2400 years
- Treta Yuga - 3600 years
- Satya Yuga - 4800 years
And two such Yugas make one Maha Yuga of 24000 years which is roughly the period for the precession of equinoxes to make one complete cycle 25772 years.
So there's a good synchronicity in considering that one year in the yuga scheme is actually one human year. And no where in any authentic scripture it says that one year is one Daiva year or Year of the GodsAnd taking one year in the yuga model as one Divya year, which ends up giving crazy big numbers which we know should be false from modern science. Hinduism is always aligned with Anumana or Modern science, it cannot invalidate it as it is one of the valid pramana.
The evolutionary process led to modern humans. Humans and their ancestors have been walking the planet for about 6 million years. Homo sapiens, who are the modern form of humans evolved 300,000 years ago from Homo erectus - Source
But if we take one year in Manusmriti Yuga scheme as one Daiva year, then
Kali Yuga - 432,000 years,
Dwapa Yuga - 864,000 years,
Treta Yuga - 1,296,000 years,
Sathya Yuga - 1,728,000 years
This means that Lord Rama and all other Rishis lived when Human beings were not even present on Earth according to Modern Science, also it simply doesn't agree with any evidence of history we have. Even the most hard core Hindus believe Lord Rama built the bridge like 7000 or so years ago and not 1,296,000 years ago.
But actually Hinduism doesn't say this, as no where in any authentic scriptures is it mentioned that one year is one Daiva year. And itIt seems that it was a later interpolation done in calculation by some Pundits. And this is what is argued by Swami Yukteshwara Giri in his famous work the The Holy Science.
But despite this glaring proofargument, today majority or Hindus and Orthodox Hindu institutions still stick to the old calculations.
So where has it said in the authentic scriptures, that a year in the Yuga schematic of Manu is actually a Daiva year? And if no authentic scripture has mentioned why is it still being followed widely in Hinduism.