Let us continue seeing how tamil languages date is taken to antiquity
Date of Tholkappiam
The dating of the earliest tamil grammatical work Tholkappiam has been debated much and it is still imprecise and uncertain and has seen wide disagreements amongst scholars in the field. It has been dated variously between 8000 BCE and 10th CE.
While most of the antediluvian datings which stem mostly from a descriptive commentary in an 12th century work called Iraiyanar AgapporuL, about the existence of three Tamil Academies, which have been rejected as being devoid of any evidence, the genuine disagreements now center around widely divergent dates lying between the 3rd BC and 10th AD. As the Tolkappiyam is often claimed as the earliest extant work of Tamil literature, the dating of Tolkappiyam is inherently tied to the dates ascribed to the birth and development of Tamil literature as a whole.
Viyapuri Pillai, the author of the Tamil lexicon and towering figure in the field dated Tolkappiyam to not earlier than the 5-6th CE.
Kamil V. Zvelebil, a Czech indologist specialised in the Dravidian languages, dates the core of Tolkappiyam to pre-Christian era.
Robert Cladwell, a 19th century linguist who, for the first time, categorised all Dravidian languages as one language family, maintains that all extant Tamil literature can only be dated to what he calls the Jaina cycle which he dates to the 8th-9th CE to 12-13th CE.
Dr.B.G.L Swamy, a renowned botanist by profession and an acknowledged historian in his own right, contends that the Tolkappiyam cannot to be dated to anything earlier than the 10th CE.
Takahashi Takanobu, a Japanese Indologist, argues that the Tolkappiyam has several layers with the oldest dating to 1st-2nd CE, and the newest and the final redaction dating to 5th-6th centuries CE.
T.R. Sesha Iyengar, an eminent scholar and expert on Dravidian literature and history, estimates the date of Tolkappiyam to have been composed 'before the Christian era'.
Dr. Gift Siromoney, an expert on ancient languages and epigraphy, estimates the date of Tolkappiyam to be around the period of Ashoka(c 300 BCE)
V. S. Rajam, a linguist specialised in Old Tamil, in her book A reference grammar of classical Tamil poetry: 150 B.C.-pre-fifth/sixth century A.D. dates it to "pre-fifth century AD".
Herman Tieken, a Dutch author, who endeavours to trace the influence of the Sanskrit Kavya tradition on the entire Sangam corpus, argues that the Tolkappiyam dates from the 9th century CE in his book, "Kāvya in South India : old Tamil Caṅkam poetry". He arrives at this result by reassigning new dates to the traditionally accepted dates for a vast section of divergent literature.
A C Burnell, a renowned indologist of the nineteenth century who has contributed seminally to the study of Dravidian languages dates the Tolk., to the 8th CE in his book.
Iravatham Mahadevan an Indian epigraphist, in his work on epigraphy published in 2003, advances a theory where he claims that Tolkappiyam could not have been written before 2nd CE.
Tholkoppiam quotes poruladhikaramsutra , a horary astrologer of 400AD.
You may say Holy God. Why such a variation. But this is the nature of dating tamil literature. People come with dates usually the oldest based on flimsy assumptions.
One of the dating methods used is the use of alphabets to determine the date. As tholkappiam talks about alphabets. Pulli theory is one of the such. The pulli is being talked about in tholkappiam ,it is a point on top of the alphabet as against the brahmi pulli which is on side. Since there is no evidence of such pulli in any inscriptions before 7th century AD, The tholkappiam is said to belong to later than 7th century AD.
Influence of Sanskrit
Influence of Sanskrit grammarians See also: Aindra school of grammar Tolkāppiyam is claimed to have been modelled on the Sanskrit grammar of the Aindra school. The preface of Ilampuranar's twelfth century commentary of the Tolkappiyam, describes it as aindiram nirainda ('comprising aindra'). This annotation was interpreted by Arthur Coke Burnell as alluding to the pre-Paninian Aindra school of Sanskrit grammar mentioned in the Ashtadhyayi. To investigate his hunch, Burnell compared the Tolkappiyam with the non Paninian Katyantra grammar and concluded that the Tolkappiyam indeed exhibited a strong influence of the non Paninian school of grammar. However, this claim has also been met with skepticism from recent researchers. The issue of the Aindra school notwithstanding, the grammar expounded by the Tolkappiyam owes a great deal to Sanskrit. The influence of various Sanskrit works like Manavadharmashastra, Arthashastra, Natyashastra and grammarians like Panini and Patanjali is evident in the Tolkappiyam. Parts of the Collathikaram are, for instance, almost a direct translation of the Sanskrit texts. The eight feelings mentioned in the Porulathikaram seem to be heavily inspired by the eight rasas or the rasa theory of the Natyashastra.
If you see the various arguments you will find that date cannot be before 8th century AD forget about before christian era.