Here's my take on it:
The Mayans believed the world would end on the date you identify. They also believed that if you danced around in big bright feathers you'd have a good farming year.
The American Indians do not seem to have a sense of time in their folklore, so "soon" could mean anytime from here to eternity. They could not even predict the return of White Buffalo Woman, although somebody predicted that if they wore special shirts and danced themselves to exhaustion that they'd be bullet-proof. (I guess he forgot to mention the need for kevlar.)
The Norse believed in Ragnarok, but never put a time to it. Pretty clever of them, since I'm SURE the world's going to die SOMEDAY.
The writings of Nostradamus are so vague that it's easy to look at them and see something in them in hindsight. It's like the Rorsarch Inkblot Test. As far as where he got the images from, remember that there was no such thing as the DEA back then. Many visions of angels and demons can be explained with bad bread (which produces chemicals found in LSD).
Edgar Cayce is one of my father's favorites. I admit his 'remote viewing' for bodily illnesses sounds pretty amazing, but that doesn't make him a prophet. Although I can't name specific instances, I believe that most of his predictions were off the mark.
Back in the 1800s the Millerites named the exact day and time of the end of the world. They got together and prayed while some of them committed suicide. The day and time came and went without the world ending. They picked another day and the same thing happened. Eventually, the Millerites dissolved into the Seventh-Day Adventists and the Jehovah's Witnesses, both of which still predict the end of the world, but never name a date.
Many psychics claim that they cannot see past the year 2000. A hundred years before, many psychics claimed they could not see beyond the year 1900. A hundred years before that it was 1800, then 1700, then 1600 and so on. They were wrong then, why would they be right this time?
One thousand years ago society prepared for the second coming. It was the Apocalypse (at least as far as the Christian world was concerned). The Millenium Mark came and went without the souls of the good Christians going up to Heaven while the pagans, Muslims, heathens, and Buddhists had their souls cast down into Hell. The "prophet" who started THIS fiasco second guessed himself and his idea of "1000 years after Christ" and amended it to read "1000 years after Christ's physical death". What was that? 1033? 1036? I know he was in his 30s when they tacked him up. Well, the 1030s also came and went without apocalyptic incident.
In the Orient, the traditional calendar is different from our Western calendar. The 21st century has already come and gone for them. I think they're in the 4600s or something. Are we to assume that Armageddon will pass the Orient by?
In the history of the planet, no doomsday prediction has come true. Society may change, but even the Industrial Revolution was a slow, gradual process.
This rock is only 4 billion years old. That's infantile on the galactic scale. What is it about the future that scares people? Every time you go to sleep you face an uncertain future. Every time you put your car on the road you're facing an uncertain future. Every moment of your life you face an uncertain future. Why should the 21st Century be any scarier?
Based on the failures and fiascoes of prophets past, there will be no Armageddon. It's been cancelled. Instead we'll have to make do with reruns of Same Sh**, Different Day.