At first a generation was defined as 20-30 years. So during World War 2 in 1939 they thought this was it. When it wasn't, they defined as a lifetime and said that those who were at least 10 years of age that year qualified as part of the Last Generation.
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| Grave of Russell & Pyramid of Giza model | 
Then the LORD said unto me, The prophets prophesy lies in my name: I sent them not, neither have I commanded them, neither spake unto them: they prophesy unto you a false vision and divination, and a thing of nought, and the deceit of their heart. Jeremiah 14:14
 

