I had to look this up. The simplified publication is called "What Can the Bible Teach Us?"
Here is the section in the back of the book.
In retrospect, it so full of holes I can't believe I ever bought any of this.
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22 WHY IS
THE YEAR 1914 SO IMPORTANT?
The prophecy in Daniel chapter 4 teaches us that God would set up his Kingdom in 1914.
The prophecy: Jehovah gave King Nebuchadnezzar a prophetic dream about a large tree that was chopped down. In the dream, a band of iron and copper was put around the tree’s stump to stop it from growing for a period of “seven times.” After that, the tree would grow again.—Daniel 4:1, 10-16.
What the prophecy means for us: The tree represents God’s rulership. For many years, Jehovah used kings in Jerusalem to rule over the nation of Israel. (1 Chronicles 29:23) But those kings became unfaithful, and their rulership ended. Jerusalem was destroyed in the year 607 B.C.E. That was the start of the “seven times.” (2 Kings 25:1, 8-10; Ezekiel 21:25-27) When Jesus said, “Jerusalem will be trampled on by the nations until the appointed times of the nations are fulfilled,” he was talking about the “seven times.” (Luke 21:24) So the “seven times” did not end when Jesus was on earth. Jehovah promised to appoint a King at the end of the “seven times.” The rulership of this new King, Jesus, would bring great blessings for God’s people all over the earth, forever.—Luke 1:30-33.
The length of the “seven times”: The “seven times” lasted for 2,520 years. If we count 2,520 years from the year 607 B.C.E., we end up at the year 1914. That was when Jehovah made Jesus, the Messiah, King of God’s Kingdom in heaven.
How do we get the number 2,520? The Bible says that three and a half times equal 1,260 days. (Revelation 12:6, 14) So “seven times” is double that number, or 2,520 days. The 2,520 days are equal to 2,520 years because of the prophetic rule “a day for a year.”—Numbers 14:34; Ezekiel 4:6.