N.H. Rev. Stat. Ann. § 507-D:5

This chapter applies to all product liability actions accruing after August 22, 1978, and, as to such actions, shall supersede any inconsistent provision of law. In addition, this chapter applies to causes of action accruing prior to August 22, 1978, upon which no action has been instituted as of August 22, 1978, except that the time for bringing such actions as specified in RSA 507-D:2 shall be computed from August 22, 1978.