The scripture which above all others had been both the foundation and central pillar of the advent faith was the declaration, “Unto two thousand and three hundred days; then shall the sanctuary be cleansed.” Daniel 8:14. These had been familiar words to all believers in the Lord's soon coming. By the lips of thousands was this prophecy joyfully repeated as the watchword of their faith. All felt that upon the events therein brought to view depended their brightest expectations and most cherished hopes. These prophetic days had been shown to terminate in the autumn of 1844. In common with the rest of the Christian world, Adventists then held that the earth, or some portion of it, was the sanctuary, and that the cleansing of the sanctuary was the purification of the earth by the fires of the last great day. This they understood would take place at the second coming of Christ. Hence the conclusion that Christ would return to the earth in 1844. SR 375.1
But the appointed time came, and the Lord did not appear. The believers knew that God's Word could not fail; their interpretation of the prophecy must be at fault; but where was the mistake? Many rashly cut the knot of difficulty by denying that the 2300 days ended in 1844. No reason could be given for this position, except that Christ had not come at the time of expectation. They argued that if the prophetic days had ended in 1844, Christ would then have come to cleanse the sanctuary by the purification of the earth by fire; and that since He had not come, the days could not have ended. SR 375.2
Though the majority of Adventists abandoned their former reckoning of the prophetic periods, and consequently denied the correctness of the movement based thereon, a few were unwilling to renounce points of faith and experience that were sustained by the Scriptures and by the special witness of the Spirit of God. They believed that they had adopted sound principles of interpretation in their study of the Scriptures, and that it was their duty to hold fast the truths already gained, and to still pursue the same course of Biblical research. With earnest prayer they reviewed their position, and studied the Scriptures to discover their mistake. As they could see no error in their explanation of the prophetic periods, they were led to examine more closely the subject of the sanctuary. SR 376.1