zahavasdad – The first day of Spring is only April 4 according to Tekufas Shmuel, which is know to be inaccurate, as is discussed at length in the Rishonim and Achronim. The calendar doesn’t use Tekufas Shmuel.
Obviously you do understand that the Tekufas Nissan is exactly when it is, as it is a physical phenomena. There cannot be a different first day of Spring according to the Jewish Calendar.
This year Pesach is March 26, and is still after the accurate Tekufah.