No problem for the Watchtower to say "about 1914". You can make up bullshit JW doctrine as you go along.
How about this.....
Satan & his demons cast out of heaven right on time in 1914 based on the WT chronology starting in 607 BCE.
However, the speed of their being cast down bent the fabric of space & time, and they actually went back in time and hit the earth as the 1908 Tungusta event in Siberia.
Satan & his demons were then able to stir up WWI, the Russian communist revolution, and then the rise of Adolph Hitler in the early 1930's. The Watchtower can then say that this portion of the the prophetic chronology is support by a fall of Jerusalem based on the secular chronology starting in 587 BCE.
The Watchtower can then just say the "last days" and start of "the generation" began with WWII and not WWI. WWII was a double witness that "the last days" had started.
This crap could have been more acceptable to JW's, than the "over-lapping" generation nonsense.