It was a Friday.
Dec 13, 1990 was a Thursday.
Tuesday
Monday
It was a Sunday.
Thursday
Dec 13th 1961 was a Wednesday.
December 13 1958 was a Saturday.
December 13 1985 was on a Friday.
December 13, 1972 was a Wednesday.
December 13, 1963 was a Friday.
February 13, 1991 was a Wednesday.
From a perpetual calendar: December 13, 1965 was on a Monday.