The International Bible Students made a mistake . They did not consider a period of 120 years that must be taken into account before Armageddon happens.
The latest prediction is for the year 2011 AD ( check this usenet group alt.religion.jehovahs-witn ) which includes the period of 120 years:
1884 AD + 120 years = 2004 AD and 7 years extra are for 7 days also from Noah's time of the Flood - Genesis 6.3;7.1-4.
The end of the world could not happened in 1914 AD or any other date set forth till such period of 120 years is shown.
The International Bible Students could provide the year 1874 AD so if we add 120 years we come to the year 1994 AD which should be the earliest prediction set forth by Jehovah's Witnesses . Their 1975 will not stand the scrutiny of the Bible as well.
Since the year 7 BC is most likely date for Jesus' birth ( it was a jubilee year ) we come to the 1994 AD ( a jubilee year ) as the first reliable prediction .
Had I knew that I would not have predicted the end of the world for 1991 AD.