From John Denton's amazing website: http://www.tangotango.org.uk/
DID THE GENTILE TIMES START IN 607 BC?
Some authorities on Bible prophecy having accepted Russell's calculations, teach that the 2,520 years of the Gentile Times started in 607 BC, when they reckon the last God approved king Zedekiah reigned over Jerusalem as God's representative king, 2,520 years from this date ends in 1914. Following are six reasons why this assumption is inaccurate.
6a) The tree vision was given to Nebuchadnezzar not Zedekiah. It related to a period starting when the Babylonian dynasty was chopped down, not God's. Yahweh sets the date for this chopping down, having an angel write on the wall the proclamation to cut down the Babylonian dynasty on the wall during the very day the dynasty is brought to its end (Daniel Chapters 4 & 5).
6b) Daniel's prophecy of 'seven times' following the cutting down of the tree could not be applied to Zedekiah in Jerusalem as Daniel explicitly says at 4:22 the tree symbolises the king of Babylon and his Dynasty.
6c) The previous vision to Nebuchadnezzar of a symbolic statue was a parallel vision of the same time period. In no way would anyone argue that the head of Gold represented Zedekiah's rulership. Both visions related to the same things.
6d) Zedekiah could hardly be reckoned as God's king. God had already arranged that the previous king Jehoiachin was removed by Nebuchadnezzar as punishment to the nation; he would hardly have replaced him with another king in contradiction of his expressed warnings (Jer 27:6,12-14,17,20-22) .
6e) Zedekiah was not anointed by God to reign as king in Jerusalem, he was appointed to the job of vassal representative by Nebuchadnezzar (2 Kings 24:17). Later he rebelled against his master Nebuchadnezzar, despite God warning him against carrying out this totally unnecessary self-destructive action. In no way can it be construed his rule was on behalf of Jehovah.
6f) The seat of God's rulership continued at Jerusalem with or without an anointed king being present. Some 600 years later, Jesus in 33 recognised that God's symbolic seat of rulership was still the temple at Jerusalem without any anointed king representing him at the time. Just before his death he presented himself at this seat of rulership as its appointed king (Luke 19:34-44) . Although the covenants changed in 33 and special favour to the Jews was extended to 36, along with the temple and city of Jerusalem, Jehovah did not tear them down until the year 70. Jesus in his signs foretold that after the temples destruction in 70 the nations would trample on literal Jerusalem, and continue to do so until the Gentile times ended, when the new temple and city would be constructed in the heavens (Luke 21:24) . Jerusalem's being trodden on, according to Jesus, did not start in 607 BC but in AD 70.