Every 5 years with the regime change, the Tamil New Year also shifts from January 14 (Month of Thai) to April 14 (Pongal). What people forget is that that is true with almost all important festivals.
Christmas was not even in December. Infact forget the month, it is still debated in which year Jesus Christ was born. (l) The new year was always in the spring (1st March) rather than 1st January. In fact the months are also numbered accordingly September (seven), October (eight), November (nine), December (deca- ten)