Smiddy3 wondered, "I didn`t know back then that this was the second time the JW`s had said 6000 years of human existance had lived on Earth ,there was a much earlier one .
Off hand i can`t remember when."
You may be thinking of 1925, but 1972 was also hinted at VERY indirectly: readers would have to do the arithmetic suggested in one of the WTB&TS books (I can't recall the title right now).