"The apostle Paul warned the church not to look for the coming of Christ in his day. “That day shall not come,” he says, “except there come a falling away first, and that man of sin be revealed.” 2 Thessalonians 2:3 . Not till after the great apostasy, and the long period of the reign of the “man of sin,” can we look for the advent of our Lord. The “man of sin,” which is also styled “the mystery of iniquity,” “the son of perdition,” and “that wicked,” represents the papacy, which, as foretold in prophecy, was to maintain its supremacy for 1260 years. This period ended in 1798. The coming of Christ could not take place before that time. Paul covers with his caution the whole of the Christian dispensation down to the year 1798. It is this side of that time that the message of Christ's second coming is to be proclaimed. GC 356.1"
"Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;"
Ellen White directly references 2 Thessalonians 2:3 in this passage.
"No such message has ever been given in past ages. Paul, as we have seen, did not preach it; he pointed his brethren into the then far-distant future for the coming of the Lord. The Reformers did not proclaim it. Martin Luther placed the judgment about three hundred years in the future from his day. But since 1798 the book of Daniel has been unsealed, knowledge of the prophecies has increased, and many have proclaimed the solemn message of the judgment near. GC 356.2"
"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."
EGW connects the unsealing of Daniel's book and the increase of knowledge to the proclamation of the judgment message, drawing a thematic parallel to Daniel 12:4.