Sunday.
Dec 13, 1990 was a Thursday.
August 13, 1990 was a Monday.
It was a Saturday.
It was a Thursday.
Tuesday.
13 May 1962 was a Sunday.
May 13 1945 was a Sunday.
May 13 1955 was a Friday.
May 13, 1986 was a Tuesday.
May 13, 1996 was on a Monday.
May 13 1954 was a Thursday.
May 13 2010 was a Thursday.