1799, 1874, 1878, 1881, 1914...
Charles Taze Russell, who had referred to himself as "God's mouthpiece", died in 1916. He left behind a legacy of time prophecies not one of which had brought the results foretold. He also left behind thousands of confused followers (Franz, Crisis of Conscience, p.204).
1918, 1925, early 1940s...
And the Watch Tower continued to make false prophecies about the ending of the current world system, couched in such terms as to brook no disagreement from its adherents, all of which proved false (or, like the book of Mormon, unverifiable, since they referred to the 'invisible' reign of Christ beginning in X year...) In writings subsequent to each of the failed prophecies the organization glossed over its failures, covered them up or toyed with its readers along the lines of 'we weren't trying to say we were sure about that date, just zealous, and anyway look at how it made you all behave so much better thinking the end was nigh' (see Franz, Crisis, 205).
In the years leading up to 1974, 1975 was proclaimed as the big one. Occasionally in speeches a cautionary note would be sounded, but the tone was full of excitement and pregnant with expectation so that the implication of certainty ended up more powerful than bald assertion of certainty would have been - especially for those fed on a diet of Watch Tower and used to doing what they were told. This paragraph is typical - just as it is typical of JW writing style (use of 'Bible' as an adjective, putting a passage to the opposite use from its actual meaning and import, random proof-texting without argumentation, etc.) Conveying its message without properly supporting it, but in a skillful fashion that leaves the desired effect in the mind of the uncritical reader.
One thing is absolutely certain, Bible chronology reinforced with fulfilled Bible prophecy shows that six thousand years of man's existence will soon be up, yes, within this generation! (Matt. 24.34) This is, therefore, no time to be indifferent and complacent. This is not the time to be toying with the words of Jesus that "concerning that day and hour nobody knows, neither the angels of the heavens nor the Son, but only the Father." (Matt. 24.36) To the contrary, it is a time when one should be keenly aware that the end of this system of things is rapidly coming to its violent end. Make no mistake, it is sufficient that the Father himself knows both the "day and hour". (WT, August 15th, 1968; in Franz, Crisis, 246.)
If only the Watch Tower heeded its own advice and ceased toying with the words of Jesus. The effect on the uncritical JW readers was to make many give up thoughts of marrying, give up their jobs, and generally uproot themselves in preparation for the end. Should we laugh or cry? That's a serious question.
Just in case you were wondering whether the Watch Tower speaks with hand-waving only (or, more charitably, with merely a commendable excess of zeal and enthusiasm), here's a moment of certainty from 1922 frozen in print:
There exist, however, well-established relationships among the dates of present-truth [coining clunky noun-adjectives as usual...] chronology. These internal connections of the dates impart a much greater strength than can be found in other chronologies. Some of them are of so remarkable a character as clearly to indicate that this chronology is not of man, but of God. Being of divine origin and divinely corroborated, present-truth chronology stands in a class by itself, absolutely and unqualifiedly correct. (see Franz, 266)
There are so many examples over the last 100 years of the mocking of those who doubt, of the disfellowshipping of those who demur, of the hearts and minds messed around by these predictions - every one of them false. It's only because the organisation covers its tracks so well (e.g. Russell's works are all conveniently out of print, past mistakes are glossed over, organisational history is rewritten or suppressed) that we don't see more people leaving the Watch Tower. May God grant that more people read Franz's works and go further, to realise what real Christian faith is.