By Kathryn Westcott
BBC News Online
A man from Arkansas, who has awoken from almost two decades in a coma, is now trying to catch up on half a lifetime. BBC News Online looks at a few ways in which the world has changed.
According to his family, 39-year-old Terry Wallis's entire frame of reference is stuck in 1984. They say that he thinks Ronald Reagan is still president but is talking non-stop to try to close the 19-year gap.
Terry Wallis was only 19 when a serious car accident plunged him into a coma. Not long before that, he and his wife Sandi had been celebrating the birth of their baby daughter.
Terry Wallis's family has hailed his recovery a "miracle"
One of the first things that may strike Mr Wallis will be the huge technological strides the world has taken.
Perhaps one of the most astonishing things he will discover is that the world around him is controlled by computers. Everything from a kitchen appliance to a car engine now has a tiny chip in it.
Personal computers were still quite basic when Mr Wallis went into a coma. The internet was still in its infancy.
In 1984, Apple Computers introduced the Apple Macintosh, the first consumer computer to use a mouse and graphical user interface (GUI). It was unveiled during a Super Bowl commercial evoking images from George Orwell's book, Nineteen Eighty-Four.
Just two years earlier, Time magazine had encapsulated the debate over the role of personal computers by asking whether they would "race off in pursuit of important ideas or lazily spend its time on more video games".
Today, such ruminations seem quaint in a world where video and music can be effortlessly downloaded from the internet and online games are the norm.
WHAT HAPPENED IN 1984
Ronald Reagan re-elected US president
First Apple Mac goes on sale
Marvin Gaye shot dead by his father
First untethered spacewalk
Michael Jackson's hair catches fire while filming Pepsi ad
In Mr Wallis's teenage days, video games were console-based novelties. Pac Man, one of the first video games to feature an identifiable character, was a big hit in the US in the early 1980s.
Today, he will no doubt be amazed by the phenomenon of massive, multiplayer online games. A popular game of this kind is Star Wars Galaxies, which enables a player to virtually live in space.
Mr Wallis will also find that such science fiction as dreams of living in space could become science fact, thanks to advances like the International Space Station. The ability for humans to live in space for periods of time brings Star-Trek-like space travel a step closer.
In other scientific strides, Mr Wallis will find that every gene in his body has been mapped and a heated debate over genetic engineering is in progress. Is it right, for example, to select the traits of our children, or transfer the genes from a fish to a strawberry to enable it to freeze better?
A defining event for many teenagers of the early 1980s was the threat of nuclear war. The Soviet Union was enemy number one and Armageddon was a subject of popular anxiety.
Remember Mel Gibson in the wastelands of Mad Max, or the Campaign for Nuclear Disarmament (CND) poster of Ronald Reagan and Margaret Thatcher, mocked up like Gone With The Wind's Rhett and Scarlett against a mushroom cloud?
In 1984, Ronald Reagan stated during a soundcheck for his weekly radio address: "My fellow Americans. I'm pleased to tell you that I've signed legislation that will outlaw Russia forever. We begin bombing in five minutes."
TOP GROSSING FILMS OF 1984
Beverly Hills Cop
Indiana Jones and the Temple of Doom
The Karate Kid
Later, and not so privately, he issued a moral imperative from Berlin to his Soviet counterpart: "Mr Gorbachev, tear down this wall!"
In November 1989, the Berlin Wall was breached and the Iron Curtain torn aside. Mr Reagan came to be seen as the victor in the Cold War.
Mr Wallis still believes Mr Reagan is president. But he has missed out on his seeing his own former governor of Arkansas, one Bill Clinton, rise to power as president.
He will also have missed out on the country's economic boom. Known as the roaring 90s, it was a period of unprecedented growth when capitalism US-style seemed triumphant. There were more jobs and technology prospered.
Recession followed in 2001 and another face of American capitalism was presented by a series of corporate scandals.
Today, Mr Wallis will find that the US has new enemies, and that like the early 1980s, there is edginess and anxiety among his fellow countrymen. He will learn about the day when a series of attacks were launched on America, killing nearly 3,000 people.
One of his priorities will be to get to know his 19-year-old daughter. They can talk about music, for one. The biggest hits of the 1980s - songs by Madonna, Michael Jackson and U2 - still get considerable airplay two decades later.