you're right steve2, all those Prophetical study books tend to mesh together. The then is finished book came out in 1969
*** yb75 p. 256 Part 3—United States of America ***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. 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. But the big point of it all is this, dear friends: Time is short. Time is running out, no question about that.’ Among other things, Brother Franz urged: “Let us make the most of the time and get in all the good hard work to Jehovah while the opportunity affords.”