To quote Paragraph 7, Page 27 of the Creation book, "It would seem reasonable that the 'days' of Genesis could likewise have embraced long periods of time- milleniums." The Society teaches "Old Earth Creationism," the idea that life may be billions of years old as scientists say, but that mankind has existed since the time of Adam 6,000 years ago.
Oddly enough, however, few Witnesses of my acqaintance understand or believe this, and hold that the six days were just that.