Just watched this and it puts into simple terms the complicated and strung together explanation of a foundation belief in the JW doctrine.
I have asked the very same question to have a JW explain 1914 to me directly from the Bible, most cant do it. Whats worse is the fact that a 1930's JW publication I have states the date to be 606BCE, and rather than adjust their prophetic date (1914), they chose to move the Historical date by one year to allow for their miscalculation, due to there being no year zero. All in this convinces me that they have a stake in keeping the 1914 date because they had mentioned it in early publications - though with the view of it being an end not the start, and the fact that WW1 occured which they like to promote as an apect of their 'sign'.
Top work though, well done all involved
CS 101