Saturday
There are only 30 days in the month of June. This "31st" which you just fabricated never existed. Therefore nothing happened :)
It was a Saturday.
November 30, 1944 fell on a Thursday.
July 30, 1943 was a Friday.
They arrived at 7:30 pm each day. -They were used from 1944-1945
April 30 1945 was a Monday.
It was a Sunday.
30 June 2010 will be a Wednesday.
30 June 1948 was a Wednesday.
30 June 1953 was a Tuesday.
June 30 1990 was on a Saturday.
June 30 2008 was a Monday.
June 30, 1950 was a Friday.
30 June 1947 was a Monday
June 30 2011 will be a Thursday.
June 30 2018 will be on a Saturday.
June 30, 1981 was a Tuesday.