There is no one single statute of limitations for wrongful termination because there are several different laws that may apply. The deadlines for filing range from 30 days to 3-4 years in certain circumstances. The majority of claims under federal law are subject to a 180 day filing deadline. You really need to consult with an attorney to determine whether you have a claim for wrongful termination and what the appropriate statute of limitations applies.
I am an experienced attorney focusing my practice on employment law in North Carolina. This post/response is not meant to constitute legal advice.