26 U.S.C. § 2504: Taxable gifts for preceding calendar periods

there shall be treated as gifts such transfers as were considered to be gifts under the gift tax laws applicable to the calendar period in which the transfers were made, there shall be allowed such deductions as were provided for under such laws, and the specific exemption in the amount (if any) allowable under section 2521 (as in effect before its repeal by the Tax Reform Act of 1976) shall be applied in all computations in respect of preceding calendar periods ending before January 1, 1977 , for purposes of computing the tax for any calendar year. In the case of gifts made to any person by the donor during preceding calendar periods, the amount excluded, if any, by the provisions of gift tax laws applicable to the periods in which the gifts were made shall not, for purposes of subsection (a), be included in the total amount of the gifts made during such preceding calendar periods. the transfer of property by gift made during a preceding calendar period (as defined in section 2502(b)); or an increase in taxable gifts required under section 2701(d), The term “net gifts” as used in the corresponding provisions of prior laws shall be read as “taxable gifts” for purposes of this chapter.