This is for those who wish an explanation of the 1874 date on historical grounds, irrespective of the truthfulness of the claims made for that date. Historically the early Adventists, Miller, Barbour, Russell - and even commentators of Christendom - had arrived at a method of interpretting the books of Daniel and Revelation known as the historicist approach. Using the day-for-a-year principle, periods of "days" were understood to refer to long periods of years - and the problem was to determine when any particular period began and ended.
Toward the end of his book, Daniel had been instructed: "But thou, O Daniel, shut up the words, and seal the book, even to the time of the end: many shall run to and fro, and knowledge shall be increased." (12:4) In the time of the end, when the book would be unsealed, its understanding would be due to the providence of God - and any significant date arrived at by the proper method could be understood to be "God's date."
William Miller was on a boat ride, and a group of clergy on their way to a conference confronted him, wanting to know how it was possible to calculate the date for the return of Christ. Miller quoted the very last verse of Daniel: "But go thou thy way till the end be: for thou shalt rest, and stand in thy lot at the end of the days." (12:13) He asked if that referred to the Second Coming. Yes, they answered, for Daniel's resurrection was expected to occur then. But when would "the days" end? Miller quoted the previous verse: "Blessed is he that waiteth, and cometh to the thousand three hundred and five and thirty days," (12:12) that is, 1,335 days. Well, came the reply, that's all well and good - but how do we know when the 1,335 days began? That gave Brother Miller an opportunity to explain.
The vision of Daniel 7 concerns four great beasts, or empires, commonly understood to refer to Babylon, Medo-Persia, Greece and Rome. The fourth beast had ten horns (understood to be the remnants into which the Roman Empire was broken - the nations of Europe), and a little horn rose up after them and subdued three. This little horn has been understood by older Protestant commentators to be the Papacy. Concerning this horn it was stated: "And he shall speak great words against the most High, and shall wear out the saints of the most High, and think to change times and laws: and they shall be given into his hand until a time and times and the dividing of time. But the judgment shall sit, and they shall take away his dominion, to consume and to destroy it unto the end." (7:25-26) The three and a half times are described in Revelation 12:6 and 14 as being 1,260 days. If we convert these into years, when did they begin and when did they end? A generation prior to Miller, something startling had occurred with regard to the Papacy. Napoleon had risen to power and his general had taken the Pope prisoner in 1798, the death of that pope occurring the next year, 1799. Thereafter, Papacy ceased to have the political power which it had previously held in Europe. Now it was a simple matter of counting backwards to arrive at the beginning of the 1,260 years.
Here, we must leave Miller behind and take up the chronology of Barbour/Russell, as our concern is with arriving at the 1874 date rather than Miller's conclusions. But, Miller got us off on the right track. We find that Barbour/Russell counted back from the year 1799 and arrived at 539 C.E. - the date that the Byzantine emperor Justinan had been reconquering the western territories of the Roman Empire and his decree went into effect that the Bishop of Rome (the Pope) be considered the chief bishop or head of the Catholic Church.
But the 1,260 years (days) are understood to be only a part of a longer period. The 1,260 day-years may have ended in 1799 (thus beginning the time of the end), but one of the angelic figures in Daniel's final chapter asks the question, "How long shall it be to the end of these wonders?" (12:6) The answer given by another figure was: "from the time that the daily sacrifice shall be taken away, and the abomination that maketh desolate set up, there shall be a thousand two hundred and ninety days," that is, 1,290 days. (12:11) The abomination that causes desolation is understood to have gone into effect in 539 C.E. with the ascension of Papacy. But further along the time line is the 1,335 days, another extension of the original 1,260 days: "Blessed is he that waiteth, and cometh to the thousand three hundred and five and thirty days." (12:12) That brings us 75 years beyond 1799, or 1874.
But Miller's original argument was that the end of the 1,335 days would bring the resurrection of Daniel, and would therefore involve the Second Coming of Christ. With the new theology that there are two classes, a heavenly and an earthly, and Daniel belonging to the earthly class would be raised sometime after Armageddon, this seems to fall apart. But if Daniel, as other Old Testament prophets, represented the Kingdom class, then those whom Daniel represented were invisibly resurrected shortly after the end of the 1,335 days. And so we have an explantion of the date 1874 as marking the invisible return of Jesus. For those who believe it is "God's date."