Quandry asked how the society came up with 1872. They were off by 100 years as shown here,
God's Kingdom Of A Thousand Years Has Approached. 1973. pp. 206, 209
It is true that the editor and publisher of Zion's Watch Tower and Herald of Christ's Second Presence calculated that the "presence" or parousia of the heavenly bridegroom began in the year 1874 C.E.
In the year 1943 the Watch Tower Bible and Tract Society published the book "The Truth Shall Make You Free." In its chapter 11, entitled "The Count of Time" it did away with the insertion of 100 years into the period of the Judges and went according to the oldest and most authentic reading of Acts 13:20, and accepted the spelled-out numbers of the Hebrew Scriptures. This moved forward the end of six thousand years of man's existence into the decade of the 1970's. Naturally this did away with the year 1874 C.E. as the date of return of the Lord Jesus Christ and the beginning of his invisible presence or parousia.
Here were some more dates of that era,
Zion's Watch Tower and Herald of Christ's Presence May 1 1881
We would like to correct this misapprehension once for all, by stating that we do not expect Jesus to come this year, nor any other year, for we believe that all time prophecies (bearing upon Jesus' coming) ended at and before the fall of 1874, and that He came there, and the second advent is now in progress and will continue during the entire Millennial age. We believe that his presence will be revealed to the eyes of men's understandings gradually during this 'Day of the Lord,' (forty years - from 1874 to 1914,) as it now is to ours; except that we, discern it through the word of prophecy revealed by the Spirit, and they will recognize his presence by His judgment upon Nominal Zion, and the World.
The Watchtower Reprints, January 15, 1892, p. 1355
The date of the close of that ‘battle’ is definitely marked in Scripture as October, 1914. It is already in progress, its beginning dating from October, 1874.
The Watchtower Reprints, July 15, 1905, p. 3576
[Charts showing 1874 date as start of times of trouble; 1914 as the end of armageddon.
Gumby