After the fact, the WTS tried to show that they tried to prevent speculation...but they kept teasing the rank and file.
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yb75 p. 256 United States of America (Part Three) ***Just think where we are in the stream of time! Its importance was deeply impressed on our minds back in 1966. God’s people then received the absorbing book Life Everlasting—in Freedom of the Sons of God. It did not take long for most of them to note the chronological chart in it that identified 1975 as the "end of 6th 1,000-year day of man’s existence (in early autumn)."
This certainly raised questions. Does this mean that Babylon the Great will go down by 1975? Will Armageddon be over, with Satan bound, by then? ‘It could’ acknowledged F. W. Franz, the Watch Tower Society’s vice-president, after posing similar questions at the "God’s Sons of Liberty" District Assembly in Baltimore, Maryland (1966). However, he added, in essence: ‘But we are not saying. All things are possible with God. But we are not saying. And don’t any of you be specific in saying anything that is going to happen between now and 1975.
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w74 6/15 p. 379 Serve with Eternity in View ***True, the most accurate Bible chronology available indicates that 6,000 years of human existence will end in the mid-1970’s. So these Christians are intensely interested to see if that will coincide with the outbreak of the "great tribulation" of our day that will eliminate all wicked ones on earth. It could. But they are not even attempting to predict exactly when the destruction of Satan’s wicked system of things will occur. They are content to wait and see, realizing that no human on earth knows the date.—Matt. 24:36.
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w74 10/15 p. 635 Growing in Appreciation for the "Divine Purpose" ***The publications of Jehovah’s witnesses have shown that, according to Bible chronology, it appears that 6,000 years of man’s existence will be completed in the mid-1970’s. But these publications have never said that the world’s end would come then. Nevertheless, there has been considerable individual speculation on the matter. So the assembly presentation "Why We Have Not Been Told ‘That Day and Hour’" was very timely.
Jehovah’s Christian witnesses are confident that God is going to bring the end of this ungodly system in HIS due time. When the "great tribulation" begins, we will be able to recognize it. So instead of speculating about a certain date, as if serving with that date as a goal, we can concentrate on the important preaching work that Jesus said his disciples would do in this time period.
And our "sights" for the future will not be on some date, but we will be serving with eternity in view, just as Jude urged Christians to do.
*** w70 5/1 p. 273 An Ingathering Affecting All Mankind ***
How close we may exactly be to the end of the present divisive system of things cannot be predicted, as Jesus reported that even he did not know the day or the hour at the time of his earthly ministry. (Matt. 24:36) However, Bible chronology which indicates that Adam was created in the fall of the year 4026 B.C.E. would bring us down to the year 1975 C.E. as the date marking 6,000 years of human history with yet 1,000 years to come for Christ’s Kingdom rule. So whatever the date for the end of this system, it is clear that the time left is reduced, with only approximately six years left until the end of 6,000 years of human history. (1 Cor. 7:29) This corroborates the understanding of Jesus’ words that the generation alive in 1914 with the outbreak of World War I would not pass away until the end comes
*** w69 2/1 p. 70 The Meaning of Present World Distress ***
More recently, the book entitled "Famine—1975!" by William and Paul Paddock said concerning today’s food shortages, on pages 52, 55 and 61: "Hunger is rampant throughout country after country, continent after continent around the undeveloped belt of the tropics and subtropics. Today’s crisis can move in only one direction—toward catastrophe. Today hungry nations; tomorrow starving nations. . . . By 1975 civil disorder, anarchy, military dictatorships, runaway inflation, transportation breakdowns and chaotic unrest will be the order of the day in many of the hungry nations."