If I were to put back on my WT hat, I would say that geology proves nothing because the age of rocks is immaterial. Genesis says that "In the beginning God created Heavens and the Earth, and that was separate from the days of creation - If you wish to disagree please direct all comments to the WTS because they said it , not me.
It is true that Archbishop Usher had calculated Adam's creation as being 4004 bce. The WTS just tweaked it to 4026 bce.
As for creative days? I never did get that point even as a loyal dub. The reasoning was just obvious speculation, and yet when you think about it, so much of their expectations centered on that assumption -
gh 60/61 (Good News To Make You Happy 1976
"6 Here we enter upon the seven “days” of creation. How long were these “days”? Much longer than twenty-four hours! The Bible tells us that “one day is with Jehovah as a thousand years.” (2 Peter 3:8) But each of these “days” of creation must be even longer than that. How do we know? Genesis 2:2 says that, after six “days” of creating, God “proceeded to rest on the seventh day from all his work that he had made.” The Bible shows that Jehovah’s ‘rest day’ still continues. For the apostle Paul writes that Christians should, through faith and obedience, do their “utmost to enter into that rest.” (Hebrews 4:9-11) The Bible count of time shows that it is now close to six thousand years since God began ‘resting’ from his creative works on earth. Just ahead of us lies the thousand-year reign of Christ, by the end of which God’s purpose of filling the earth with a happy human family will have been accomplished. God’s ‘rest day’ will then end. This would indicate that this ‘rest day’ would be of seven thousand years’ duration. (Genesis 1:28; Revelation 20:4) It is reasonable to conclude that each of the six preceding “days” of creation would occupy similar periods of time, during each of which Jehovah carried out a further stage of preparing earth to be man’s future home. As we now observe how He did this, we should truly appreciate the force of the psalmist’s words: “How great your works are, O Jehovah! Very deep your thoughts are.”—Psalm 92:5.
Creation Book p27 1985
7 “Day” as used in the Bible can include summer and winter, the passing of seasons. (Zechariah 14:8) “The day of harvest” involves many days. (Compare Proverbs 25:13 and Genesis 30:14.) A thousand years are likened to a day. (Psalm 90:4; 2 Peter 3:8, 10) “Judgment Day” covers many years. (Matthew 10:15; 11:22-24) It would seem reasonable that the “days” of Genesis could likewise have embraced long periods of time—millenniums. What, then, took place during those creative eras? Is the Bible’s account of them scientific? Following is a review of these “days” as expressed in Genesis.