Saturday.
June 13, 1975 was a Friday.
February 13 1975 was on a Thursday.
August 13, 1975 fell on a Wednesday.
May 13, 1975 fell on a Tuesday.
13 December 2001 was a Thursday.
December 13 1956 was a Thursday.
December 13 1999 was on a Monday.
December 13 1985 was on a Friday.
December 13 2014 is a Saturday.
December 13 1989 was a Wednesday.
December 13 1919 was a Saturday.
December 13 1985 was a Friday.