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 1966 was a Tuesday.
May 31, 1976 was a Monday.
May 31 1947 was a Saturday.
May 31, 1952, was a Saturday.
May 31 1996 was a Friday.
May 31 2010 was a Monday.