They are NOT "just wrong", they are deceptive.
"The Watchtower has consistently presented evidence to honesthearted students of Bible prophecy that Jesus' presence in heavenly kingdom power began in 1914." Watchtower, 15. Jan. 1993, p. 5, para. 3
However, the Watch Tower Society actually taught that the presence had begun in 1874: W May 1881, WTR p.223, W Sept. 1898, WTR p.359, W 01. Jan. 1910, WTR p.4543, W 15. Feb. 1928, p.54, para. 24. Other pre- and post-1914 statements indicate that the teaching promulgated by the Watch Tower Society had been that Jesus' reign in heavenly kingdom power began in 1878: e.g. W Dec. 1879, WTR p.58, W 15. Dec. 1892, WTR p.1484, W 15. Nov. 1916, WTR p.5990.
"Based on what [Jesus] said, along with the words of Daniel and John, Jehovah's witnesses pointed to the year 1914, decades in advance,* as marking the start of 'the conclusion of the system of things.' " Awake! of 22. January 1973, p. 8, para. 4
However, the Watch Tower Society actually taught that the "time of the end" began in A.D. 1799: W Nov. 1890, WTR p.1258, W 01. Nov. 1914, WTR p.5565, The Harp of God, p. 229-234, W 01. Dec. 1928 p. 25, para. 13.
The Watch Tower Society has knowingly lied about its history.