Wednesday
Dec 31 2013 is a Tuesday.
Tuesday
It was a Wednesday.
Friday
December 31, 1953 was a Thursday.
December 31, 1959 fell on a Thursday.
May 31, 2003 fell on a Saturday.
December 31, 2003 fell on a Wednesday.
December 31st, 1985 fell on a Tuesday.
Friday
October 31, 2003 - Halloween - fell on a Friday.
31 days.