The WTS has conditioned the rank and file to accept certain doctrines at a later time.
Researching 1975, I found that numerous times before 1966 the WTS talked about 6,000 years of human history nearing its end. JWs know that the 1,000 year reign had to come within the 7,000 year long creative day and could do the math. It wasn't until 1966 the WTS really started connecting it to 1975, only 9 years away. It will be interesting to see what the WTS does as it gets within 9 years of 2034.
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w50 5/1 p. 136 "Whatever Else You Get, Get Understanding" ***This understanding has to cut through every human tradition and base, lustful craving that the human creature has been cultivating for the past 6,000 years
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w50 9/1 p. 292 Victory over Death ***To sum up, death has been having its day for nearly 6,000 years. Soon life will have its day forever.
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w51 1/1 p. 27 The Christian’s Sabbath ***Besides, from such sciences as geology it appears that both plant and animal life have been on this earth far more than 6,000 years. Note too that the entire period of creation is referred to as "the day that Jehovah God made earth and heaven". (Gen. 2:4, AS) A day in the Bible is not always 24 hours long; 7,000 years for each of the creative days as well as the rest day is consistent with the Scriptures.—2 Pet. 3:8.
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w51 5/1 p. 276 Making a Success of Marriage ***For nearly 6,000 years the institution of matrimony has been in operation.
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w52 10/15 p. 631 God’s Way Is Love ***It shows how he has dealt with man for the past 6,000 years, blessing and guiding obedient men up to this present time.
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w53 7/15 p. 430 Launching the Kingdom Government ***For nearly 6,000 years, yes, right down to our present generation, Jehovah has allowed Satan to remain to prove his defiant challenge. Satan has failed! Now his time is up!
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w54 3/1 p. 141 Repairers and Restorers of True Religion ***It has been slandered and men have made it a treasonable offense to practice it. Indeed, during the nearly 6,000 years of man’s existence on this earth there have been many occasions when true religion hardly survived the terrific onslaughts made against it.
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w54 3/1 p. 144 Repairers and Restorers of True Religion ***The enormity of this crime can be understood only when we consider the nearly 6,000 years of sinning, wickedness, sickness, sorrow, suffering and death inflicted on the human race.
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w54 7/1 p. 390 Why God Permits Evil ***God has permitted Satan to remain for the past 6,000 years only as Jehovah told Pharaoh, ‘to show you my power and to have my name proclaimed in all the earth
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w54 8/15 p. 496 The Power of Hope ***That sublime hope, first disclosed almost 6,000 years
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w55 2/1 p. 95 Questions from Readers ***Such then figure that from Adam’s creation, now thought to be the fall of 4025 B.C., why, six thousand years of God’s rest day would be ending in the fall of 1976. However, from our present chronology (which is admitted imperfect) at best the fall of the year 1976 would be the end of 6,000 years of human history for mankind, 6,000 years of man’s existence on the earth, not 6,000 years of Jehovah’s seventh seven-thousand-year period. Why not? Because Adam lived some time after his creation in the latter part of Jehovah’s sixth creative period, before the seventh period, Jehovah’s sabbath, began.
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w56 8/15 p. 498 Maintaining Integrity ***For Jehovah will wipe out all worldly nations in his impending war at Armageddon and thereby, at last, after waiting 6,000 years, vindicate his holy name.
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w60 7/15 p. 422 The Gathering Storm of Armageddon ***Satan and his demonic and human organization, responsible for 6,000 years of increasing woe, must be destroyed.
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w61 6/15 p. 378 The Seventh Day—A Sabbath of Rest ***Since the seventh creative day has proved to be thousands of years in length, nearly 6,000 years having elapsed since Adam’s creation, and since Bible prophecy proves that we are living in the time of the end of this wicked system of things immediately preceding the restful 1,000-year Kingdom reign of Christ, it is reasonable to conclude that this great rest day would be complete with 7,000 years. The 1,000-year reign of Christ would logically be included in this 7,000-year rest day of God. This means the seventh creative day is in itself a week of 1,000-year days. Because Jehovah’s name will be vindicated during this time and his purposes for the earth and for man completely fulfilled, the day is sacred. His blessing of it will be manifested in the 1,000-year reign of the Messiah.