I found a reference in the Reasoning (rs) book, page 88, dating back to 1989 that begins to open the door to a change in thought. Says in essence a creative day was at least thousands of years long. References a quote about some rock formations being billions of years old.
I thought there was some reference to this in the book Aid to Bible Understanding, but didn't find it when thumbing through the spots where I expected to find something.
I know I remember reading a secondary article maybe in Awake that peaked my interest in that change. I marveled even then that they were sneaking in a change of thought.