For me, the U.S. ice hockey gold medal victory in the Olympics was the turning point - especially the upset of the Soviet Union team. That occurred towards the end of February of 1980, and it was at that point that the stink of the 1970s was flushed down the toilet - like an especially bad case of diarrhea.
I remember getting so caught up in that event that I drove to Winthrop, MA to see Mike Eruzione's victory parade as that song "99" by Toto played on the radio.
The 1980s decade was perfected bookended on Christmas Day of 1989 when the Ceausescu's were executed in Romania. That was the unofficial kickoff of the rapid fall of the Iron Curtain in Europe and the disintegration of the Soviet Union.
In between, well, those were some pretty good years. Lots of prosperity, eight years of Ronald Reagan, millions of high tech jobs being created, the future looked pretty darn bright back in the 1980s. If only I could go back to say, 1985, with $10,000 to invest in Microsoft!
It's a shame that people under the age of 40 never got to experience the optimism that used to exist here in the United States.