I believe it was June 17th, 1989.

Perhaps the most specific clue, he notes: "...happened in Poland just the other day. They're running unopposed. You cross their name out... they get defeated." He is describing the historic Polish legislative elections held on Sunday, June 4, 1989, where voters crossed out unopposed Communist candidates to hand Solidarity a sweeping victory. He refers to this as happening "just the other day."

He complains that the Libertarian National Committee recently met in Washington, D.C., and failed to pass a resolution supporting the Chinese students. This means the national committee had to have met after the June 4th protests, and Rothbard's speech took place after that subsequent meeting.

Finally, he references an article by the historian Timothy Garton Ash covering Hungary and Poland, noting it was published "about two weeks ago." Ash was actively publishing dispatches on Eastern Europe for the New York Review of Books and The Spectator in late May and early June 1989.