The authority of the Watchtower as God’s only channel of communication is based on the teaching that Jesus arrived invisibly in 1914 to judge Christendom and that he in 1919 selected the Watchtower as the only spokespeople for him. The date 1914 is calculated as being 2520 years from the year 607 BCE, a period referred to as “the gentile times” were no kings ruled on the throne of David. This is based on chapter 4 of the book of Daniel.
Jerusalem was destroyed in 587 BCE, not 607 BCE
It’s attested by secular historians
There is not a single reputable historian that agrees that Jerusalem was destroyed in 607 BCE. The Watchtower is the only one who claims this and bases it on extremely flimsy evidence.
It’s attested by Watchtower literature
The Watchtower gives the length if the reigns of the kings of Babylon. When you add them up and calculate it, you also end up with a date of 587 BCE.