Tuesday.
October 31, 2011, will be a Monday.
August 31, 2011 was a Wednesday.
December 31, 2011 is a Saturday.
Saturday
31 May 1958 was a Saturday.
May 31 1967 was a Wednesday.
May 31, 1932 was a Tuesday.
May 31, 2006 was a Wednesday.
May 31, 1983 was a Tuesday.
May 31 1966 was a Tuesday.
May 31, 1976 was a Monday.
May 31 1947 was a Saturday.