For purposes of this section, in the case of property the acquisition of which by the taxpayer resulted under section
1034 (as in effect on the day before the date of the enactment of this section) in the nonrecognition of any part of the gain realized on the sale or exchange of another residence, in determining the period for which the taxpayer has owned and used such property as the taxpayer’s principal residence, there shall be included the aggregate periods for which such other residence (and each prior residence taken into account under section
1223
(6) in determining the holding period of such property) had been so owned and used.