Here is a letter dated May 12,1975 from the governing body
The following quote is from that letter
Quote
While the beginning of the seventh "day" is admittedly tentative, the end of the six thousand years of man's history in the fall of 1975 is not tentative, but is accepted as a certain date. So in good faith and with right motive to enhance Bible education, the date of 1975 has been presented with confidence, as one of considerable significance. While some outsiders have come to be quick in denouncing the Society, yet we calmly wait fot the completion of this Biblical year of 1975 as we continue to strengthen ourselves spiritually. From Jehovah's viewpoint and his eternal purpose for the earth, the completion of six thousand years of man's residence on this earth is bound to be important.
End quote
Here is the link where the letter originates from
http://www.jwfiles.com/x-files/78letter.htm
The above letter states the end of man's 6 thousand years ended in 1975. The society presented 1975 with "confidence " just as rutherford presented 1925 with "confidence"
No wonder the JW left after 1975!