I know it ended on January 1, 2001, but historians often talk about a “Short Twentieth Century” that started in 1914 and ended either in 1989 or 1991 with the fall of the Soviet sphere.
Personally I think you could pick a lot of dates for the “short” 20th century’s end.
1979 would be the earliest possible date, I would say. That was the year the first cell phones were sold in Japan and also the beginning of modern Islamism. It’s also about the earliest time that the average person could buy a home computer, if they wanted to shell out the money. 1979 also represented the noontide of the American middle class and, I would argue, the high point of world socialism as it was just before Solidarity formed in Poland, Tito died, Reagan won the presidency and was right at the beginning of China’s renouncement of communism. Tim Berners Lee also started writing ENQUIRE around then which would eventually become the World Wide Web.
Another possible date would be January 1, 1983, the date that the ARPANET officially adopted TCP/IP, hence creating the Internet. 1983 also marks the first cell phone service in the United States as well as the war in Grenada which paved the way for Desert Storm and the current wars.
1989 is a good date too being that the World Wide Web was fully conceived of at this point, the first commercial ISPs went online and Al-Qaeda started. 1989 is also when the first digital cameras became available to buy. And obviously you had the opening up of the Berlin Wall and German border.
1991 marked the end of the Soviet Union and India’s “opening up” to the world as well as the rise of Grunge music and the official release of the Web, which was invented on paper in 1989 and tested for the first time in late 1990.
1994 is the date I would choose, though. This was not only the last year that was generally “pre-Internet” but it also marked the last Red Army and American troops leaving Germany. Coincidentally, if the Gospels are to be believed the 2,000th anniversary of Christ’s birth likely took place in or very close to 1994.
2001 and 2007 are both good dates too, for obvious reasons of 9/11 and the beginning of the Great Recession. What do you think?