"Thai piranthaal Vazhi pirakkum", yes this is a phrase commonly used by Tamils since the Sangam Period (2,000 year back). Why not "Chithirai piranthall vazhi pirakkum", if Chithirai is the New Year of the Tamil people.
Thai Pongal is the New Year for the Tamil speaking people. Allow me to send my sincere and best wishes to one and all Tamils. I also wish them a very Happy and Prosperous Tamil New Year and Joyous Pongal.