The WTS did write with certainty concerning the 1914 generation and the last days.
*** gc pp. 21-22 Is There a God Who Cares? ***
Wickedness Soon to End
27 The human family desperately needs a change for the better. In fact, we need an entirely new system. As sociologist Erich Fromm admitted, the evils in society can be corrected “only if the whole system as it has existed during the last 6,000 years of history can be replaced by a fundamentally different one.” That is exactly what God has in mind! When his allotted time period is up, God has guaranteed to crush out of existence the entire present wicked system of things, along with those who prefer it. “All the wicked ones he will annihilate.”—Psalm 145:20.
28 When will this take place? Very soon, because God’s Word shows that the unprecedented troubles that have struck the human family since the first world war began in 1914 make up a sign identifying what is called in the Bible “the last days.” The Bible foretold that in these “last days” there would be world wars, mounting crime, hunger, disease epidemics, wanton pleasure-seeking by the majority, the turning away from belief in God, religious hypocrisy and decay, and many other events. These would be like the lines of a fingerprint, identifying with certainty our generation as the final one in which God would tolerate such terrible conditions. Jesus prophesied that our time would indeed see the end of the system of things now dominating the earth.