Actually, the 1874 date was based on the 1335 days prophecy of Daniel, the "double" parallels, and the jubilee cycles. 6,000 years from Adam's creation, according to Barbour/Russell's chronology, does not end in 1874, but rather in 1872 (or using the whole year method of years from fall to fall, the beginning of 1873). Russell allowed two years from Adam's creation to his disobedience, which he believed happened 6,000 years before 1874.
Neither Barbour nor Russell replaced 1874 with 1914, as many on the internet have claimed, since Russell believed -- until his death -- that Christ had returned in 1874. Rutherford also for many years after Russell's death taught that Christ had returned in 1874 until about 1928 or 1929, about whch time he began to claim that Christ had returned in 1914, and began using the 1335 days and the other days of Daniel as alleged proofs of events related to his new organization.