From a US perpetual calendar: September 20 1989 was on Wednesday.
June 20 1989 was a Tuesday.
May 20, 1989 was a Saturday.
March 20 1989 was on a Monday.
August 20, 1989 fell on a Sunday.
April 20, 1989 fell on a Thursday.
September 20 1951 was a Thursday.
20 September 1988 was on a Tuesday.
September 20, 1993 was on a Monday.
20 September 1999 was a Monday.
September 20 in 1969 was a Saturday.
September 20 1952 was a Saturday.