42 U.S.C. § 7514a

section 7514(a) of this titleImplementation plans required under shall provide for attainment of the relevant primary standard as expeditiously as practicable but no later than 5 years from the date of the nonattainment designation.

section 7514(b) of this titleNovember 15, 1990Implementation plans required under shall provide for attainment of the relevant primary national ambient air quality standard within 5 years after .

November 15, 1990Implementation plans for nonattainment areas for sulfur oxides or nitrogen dioxide with plans that were approved by the Administrator before , but, subsequent to such approval, were found by the Administrator to be substantially inadequate, shall provide for attainment of the relevant primary standard within 5 years from the date of such finding.