Thanks Vidqun and others.
So in a nutshell:
Its the 1914 chronology + 3 1/2 years + some religiocentric events that are not in the bible ("Does it have to be in the Bible" Rattigan said!!).
Yes, there's a gap between 1918 and 1919. October 1914 + 3.5 years = April 1918!!!!
This glaring gap between 1918 and 1919 is filled over by reliance on non-Biblical, religiocentric events, ie, the end of WW1 followed by the release of Judge Rutherford and his Watchtower colleagues from prison.
1918 wasn't chosen for the date Jesus selected the Watchtower as his FDS because in 1918 Joseph Rutherford and his mates were arrested!
This is the foundation that the new 1919 understanding rests on - the post-war release from prison in 1919 of Joseph Rutherford and his buddies, a totally non-biblical event.