“The scripture which above all others had been both the foundation and the 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 repeated as the watchword of their faith. All felt that upon the events therein foretold 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. They understood that the cleansing of the sanctuary was the purification of the earth by the fires of the last great day, and that this would take place at the second advent. Hence the conclusion that Christ would return to the earth in 1844.
“But the appointed time had passed, and the Lord had not appeared. 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 except that Christ had not come at the time they expected Him. They argued that if the prophetic days had ended in 1844, Christ would then have returned 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.
“To accept this conclusion was to renounce the former reckoning of the prophetic periods. The 2300 days had been found to begin when the commandment of Artaxerxes for the restoration and building of Jerusalem went into effect, in the autumn of 457 B.C. Taking this as the starting point, there was perfect harmony in the application of all the events foretold in the explanation of that period in Daniel 9:25–27. Sixty-nine weeks, the first 483 of the 2300 years, were to reach to the Messiah, the Anointed One; and Christ’s baptism and anointing by the Holy Spirit, A.D. 27, exactly fulfilled the specification. In the midst of the seventieth week, Messiah was to be cut off. Three and a half years after His baptism, Christ was crucified, in the spring of A.D. 31. The seventy weeks, or 490 years, were to pertain especially to the Jews. At the expiration of this period the nation sealed its rejection of Christ by the persecution of His disciples, and the apostles turned to the Gentiles, A.D. 34. The first 490 years of the 2300 having then ended, 1810 years would remain. From A.D. 34, 1810 years extend to 1844. ‘Then,’ said the angel, ‘shall the sanctuary be cleansed.’ All the preceding specifications of the prophecy had been unquestionably fulfilled at the time appointed.”
Ellen G. White, The Great Controversy, 409, 410.