I was never a witness, I joined this site after my wife started studying with them, and I got upset over some of the things that resulted from that. However, I grew up in a similar high-control group called the Worldwide Church of God. Much like the witnesses, in the mid 70s ( I forget the exact year, I was only in elementary school in those days, but it may have been 75, just like JWs), there was a big push toward the end being at hand, the Great Tribulation is coming, etc etc. I remember when this flopped, that a lot of people began speculating as to just what happened, and when the 'REAL' end would come.
Everybody had their own pet theories. One that I recall, was that it would be whatever the failed year was, +3. So assuming the WCG failure was in 75 just like the JWs, then 75+3 = 78. The reasoning being, that since Christ was actually born in 3 BC or thereabouts, that there was a 3 or even 4 year 'fudge factor', depending on whether you counted a year zero or not. Well, that came and went. Another pet theory of many was that it would be 1999, because 999 upside down was 666, and because it was very close to being 2,000 years (Many believed that time was divided into eras; 2,000 years roughly pre-flood, 2,000 more flood-Jesus, then 2,000 years Jesus-Armageddon).
I'm now an atheist, but still have sort of an intellectual curiousity into what people believe about this, it's not only the JWs who think doomsday is right around the corner. But the doomsday prophets are running out of believable dates-when will the last date be here that can still be supported biblically? When I was still a believer, I thought surely that the very last possible year would be 2004 or 2005 at the latest, after all it was 2000 years plus a few for a safety margin. According to the wikipedia entry on Anno Domini (link and quote below), there is possibly as much as an 8-10 year difference in accuracy, though. However you look at it, and whatever (in)accuracies and overlaps there are, surely we are running out of time for ANY biblical support of a 6,000 year "reign of Satan" followed by Armageddon and a 1,000 year millenium. Anybody got their own theories? And what happens when people realize this? Do they go on believing on faith anyway, or does Christianity quietly begin to fade away?
http://en.wikipedia.org/wiki/Jesus
"It is hard to date Jesus' birth because some sources are now gone and over 1900 years have passed since the Gospels were written; however, based on a lunar eclipse that the first-century historian Josephus reported shortly before the death of Herod the Great (who plays a role in Matthew's account), as well as a more accurate understanding of the succession of Roman Emperors, Jesus' birth would have been before the year 3 BC/BCE."
http://en.wikipedia.org/wiki/Anno_Domini
"Another calculation had been developed by the Alexandrian monk Annianus around the year AD 400, placing the Annunciation on March 25, AD 9 (Julian) — eight to ten years after the date that Dionysius later calculated. This Era of Incarnation was dominant in the East during the early centuries of the Byzantine Empire, and is still used today in Ethiopia, accounting for the 8 or 7-year discrepancy between the Gregorian and the Ethiopian calendar."