http://lets-watch.com/gentiletimes.html
They have botched their chronology so bad just to come up with 1914-1918.
This modern day deception concerning the gentile times began in 1823.
1823 Rev John Brown realizes that the period is 2520 years long and using erroneous secular dates, believes it started in 604BC which he claims is the accession of Nebuchadnezzar. He calculates that the 2520 years would end in 1917AD if they started in 604BC.
In 1875, Nelson Barbour calculates that the 2520 years start in 606, this being 70 years before 536 when he thought the Jews rebuilt the altar .He miscalculates (He forgot that there was no 0 BC, it went 1 BC then 1 AD !) that the 2520 years end in 1914
In 1876, Charles T. Russell publishes the same in his Bible Examiner.
Russell publishes " Zion's Watchtower and Herald of Christ presence". From this small beginning we have what today is the Watchtower Bible and tract society, publishers of the Watchtower and awake magazines. They still hold to the date of 19 14, as being the return of Christ, (but invisibly).
And all their claims of authority rest on this date.