This text is from the WTB&TS publication “God’s Kingdom of a Thousand Years Has Approached”- 1973, pages 206-207.
THE CORRECTING OF A MISUNDERSTANDING
48 It is true that the editor and publisher of Zion's Watch Tower and Herald of Corpses Presence calculated that the "presence" or parousia of the heavenly Bridegroom began in the year 1874 C.E. Also, that the date of the first man's creation by Jehovah God was in the year 4128 B.C.E., which meant that six thousand years of man’s existence on the earth ended in the year 1872 C.E., as calculated by Russell and his associates. This reckoning began to be announced on the front page of Zion's Watch Tower and Herald of Christ’s Presence beginning with the issue of July 1, 1906, and this practice continued down through the issue of September 15, 1928. For instance, on the first of such mentioned issues appeared the date of issue: "July 1, A.D. 1906- A.M., 6034"; whereas the dating of the last mentioned issue was: "Anno Mundi 6056- September 15, 1928." The Anno Mundi or "Year of the World" date was calculated to be the year 4128 before our Common Era.
49 Two years, however, were allowed for the innocence of the perfect man and woman in the Garden of Eden before sin entered, and hence the year of sin's entrance was calculated as 4126 B.C.E. This resulted in their calculating six thousand years of sin as ending in 1874 C.E., in which year also, in the autumn, the seventh millennium began, for the instigator of sin, Satan the Devil, to be bound and cast into the bottomless pit and for Christ to start reigning for the foretold thousand years. This meant that the year of the start of Christ's reign was also the year of his return and the beginning of his invisible presence or parousia.
The book goes on to explain how 100 years had been 'misplaced' somehow, and the end of 6,000 years of man's existence would actually be in the 1970's.
I remember 'studying' this book every Tuesday night for a LONG hour, and I thought then what a lot of bunglers the WTS were. I never got baptized...