Section 1250(a) of the Internal Revenue Code is modified as follows:

1. (a) The date “December 31, 1970” is substituted for “July 24, 1969,” and “December 31, 1969.”
2. (b) The date “January 1, 1971” is substituted for “January 1, 1970.”
3. (c) The date “December 31, 1976” is substituted for “December 31, 1975.”
4. (d) The date “January 1, 1977” is substituted for “January 1, 1976.”