I once had conversation with the WTS about this question. Primarily, my question was: Why do they claim that the "seven times" started at the death of governor Gedaliah and NOT at the death of the last King, Zedekiah. They say that there was no King on Jehovah's throne for "seven times", so this period should have started at the death of the last King. Gedaliah was only a governor, and there have been other governors in Jerusalem since them.
I added the question about the World War. In August, it started. In October, Jesus began ruling as heavenly King, and SOME TIME AFTER THAT, he cast out Satan from heaven, and AFTER THAT, Satan caused World War I. This does not work out. I claimed that King Zedekiah was killed in July, so it would perfectly fit the start of World War I to count the "seven times" from Zedekiah's death.
The reply that I got was very disappointing. Basically they claimed that the "seven times" must have started at Gedaliah's death because it was always written like that in the Watchtower, even in very old issues. Their main argument was that Jerusalem's devastation started after Gedaliah's death.
I wrote them that their explanation did not satisfy me. In their reply they told me that they cannot say anything else regarding that topic, and they sent me an article about a sister who waited for decades until some doctrine was changed.