Astronomical data recorded by Valmiki has been studied by many.
In the dating of Ramayana there are two major candidates that have come up - around 5,000 B.C. and around 7,000 B.C.
The copper plates of the Pandyan Kings recovered from a place called Sinnamanur in Tamilnadu make a mention of the ten hooded Ravana who was overpowered by a Pandyan King.
While tracing the genealogy of Pandyans, these inscriptions make a specific reference to an earlier Pandyan (name not mentioned) to have made Ravana buy peace
From verse 5 at -
South Indian Inscriptions Volume_3 - Pandya Copper Plate Grants Inscriptions from Sinnamanur @ whatisindia.com
At the plates it says in Sanskrit -"Dasaanan sandheepa rakshakaara"
and says in Tamil - "dasavathanan saarbaaka sandhu seithum".
Ancient Pandyan Kings are known to have dwelled during the time of first Tamil Sangam around 5,000 BC when the Kingdom was called Thennan Desam (country of the southeners).
Valmiki's Ramayana refers to the location of Kavatapuram, the capital city of the Pandyan Kings.
While giving instructions to Hanuman and other vanaras on how to proceed to the southern direction, Shugreeva narrated the places that they would encounter en route. In that context he said that after crossing the river Kaveri, Agasthya's abode and then river Tamraparani, they would reach the Kavatam of Pandyas!
( कवाटमॠपाणà¥à¤¡à¥à¤¯à¤¾à¤¨à¤¾à¤®à¥ – Valmiki Ramayana, chapter 41 -19)
This Kavatam was the capital of Pandyans during the 2nd sangam period, It was submerged in the 3rd deluge that happened 3500 years ago.
Regards,
Virendra