Period for which exemption effective

An exemption granted to any individual pursuant to this subsection shall apply with respect to all taxable years beginning after December 31, 1950 , except that such exemption shall not apply for any taxable year—

(A) beginning (i) before the taxable year in which such individual first met the requirements of the first sentence of paragraph (1), or (ii) before the time as of which the Commissioner of Social Security finds that the sect or division thereof of which such individual is a member met the requirements of subparagraphs (C) and (D), or

(B) ending (i) after the time such individual ceases to meet the requirements of the first sentence of paragraph (1), or (ii) after the time as of which the Commissioner of Social Security finds that the sect or division thereof of which he is a member ceases to meet the requirements of subparagraph (C) or (D).