The day of the week that June 20 is on depends on the year it is. In 2011, June 20 is on a Monday.
20 September 1988 was on a Tuesday.
June 20 1950 was on a Tuesday.
20 June 1958 was a Friday.
June 20 1961 was a Tuesday.
June 20 1935 was a Thursday.
June 20, 1964 was a Saturday.
June 20 1989 was a Tuesday.
June 20, 1973 was a Wednesday.
June 20, 1998 was a Saturday.
June 20, 1970 was a Saturday.
20 June 1983 was a Monday.