Over the course of a few years, and thanks to many on this board, I have assembled a history of the Watchtower's most relevant articles that show the development of the 70 years, 607 B.C.E. and how these ultimately get calculated to reach "the last days" with the appointment of the "faithful slave".
The following link contains a PDF with very little commentary and minimal notes. The purpose of this document is not to openly attack the chronology but to let the inconsistencies and, in some cases, outright lies speak for themselves. Therefore, the reader still needs to add up what this really means. However, the document can fill a need that many on this board have to address this key issue with their loved ones.
In many cases, excuses for the Society and its teachings are claimed by both witnesses and the Society itself. However, these excuses vanish if it can be proven quantitatively that it is impossible for the Society to have been appointed by Christ...even assuming if all the secondary fulfillment concepts were true. The flawed chronology and the flawed interpretation and application of the 70 years show that this is just another religion and that the bible is not written as a code and riddle that men in Brooklyn were appointed to decipher to their own benefit.
I hope this document helps...
You will note that the page numbers start a 30, this is because this is part of a larger document (formatted in the same fashion) that I will post in the future.