7 May 1971 was a Friday.
7 July 1971 was a Wednesday.
Thursday October 7, 1971
December 7, 1971 fell on a Tuesday.
January 7, 1971 fell on a Thursday.
Monday
It was a Sunday.
This isn't really a math question but the answer is Sunday
7 May 1945 was a Monday.
7 May 1948 was a Friday.
May 7 1949 was on a Saturday.
May 7 1978 was on a Sunday.
May 7 1977 was on a Saturday.