There's lots of this information in written form out there about 607 BC. All it takes is a little googling.
https://ad1914.com/history-of-the-doctrine/
https://jeffro77.wordpress.com/index/607-for-dummies/
http://www.jwfacts.com/watchtower/607-587.php
And this is a synopsis of each of the videos I linked to above: www.jwlove.org/607bc
We've had plenty of debates with JW apologists on this forum about this very subject.