There is some evidence that Rutherford first mentioned 1914 as the beginning of christs second coming in the 1930`s.
"Some evidence" implies that the question is not resolved or in some way in doubt.
It's not....
The dismantling of Barbour/Russell dates has been meticulously documented by Crompton, Penton and various other scholars
The crowning of Jesus as King of God's kingdom was moved forward 40 years to correspond with the end of the Gentile Times in the year 1920 (The Watch Tower July 1, 1920 p. 96) which was just a couple years after Rutherford became President
The resurrection of the saints (first resurrection) was moved forward ~40 years (1878 to 1914) in the year 1927 (Light Volume I p. 226)
The very last clear reference to 1874 as the start of the Parousia can be found in the book Prophecy pp 65-66
The first clear reference in The Watchtower to 1914 as the beginning of the Parousia occurs in the December 1, 1933 edition page 362. That this change was about to be made official can be seen in The Golden Age, April 30, 1930 pp 503 - 504 and Light, Book I, p 74)
At this point, virtually every time element of the Barbour/Russell eschatology had been modified. The only thing left was the idea that 1873 marked the end of 6000 years since Adam's creation
Perhaps this chart would be helpful:
