I think we should focus not on the 607BCE issue but rather on their different views of 1914 in the past 130 years. As Simon says no one wants to do the math.
Here are the basic metamorphosis that 1914 went through:
!) The end was a period of time from 1799 to 1914. Armageddon was a 40 year period between 1874 and 1914 which was supposed to have been a period of social anarchy. The Millennium would begin in 1914.
The earthquakes, famines and wars predicted in Matthew 24 were fulfilled in the past 1800 years (from the point of view in the late 1880s) since that prophecy was made.
2) Then, sometime after that failed to come about, they said that the end would occur within the lives of those who witnessed the events of 1914.
Throughout the 1970s to early 1990s the age of reason of those who witnessed the events of 1914 was considered to be young adults. But later they shrunk the age down to children but indicated that infants were included. When that failed they changed that to infants born in 1914.
3) Now we got the "overlapping generations".