It was a Tuesday.
06.09.1975 is June 9 1975, a Monday, in the US, and is 6 September 1975, a Saturday, in most other countries.
February 9, 1975 was on a Sunday.
August 9, 1975 fell on a Saturday.
July 9, 1975 fell on a Wednesday.
May 9, 1975 fell on a Friday.
It was a Saturday.
Thursday
9 September 1954 was a Thursday.
September 9 1950 was on a Saturday.
September 9 2009 was a Wednesday.
September 9 2009 was a Wednesday.
September 9 2002 was a Monday.