In Daniel 8 and 9, God revealed two prophecies that overlap and share a starting point. The first prophecy was the 2300 prophecy which gave the date for the beginning of God’s final judgment. And the second prophecy was the 70-week prophecy. This week prophecy predicted the first coming of Jesus, time of His death, and the time of the judgment of the Jews that rejected Christ.
The cleansing of the sanctuary
The two prophecies begin when the saint asked how long will God’s people and heavenly sanctuary would be trodden under foot? The angel replied, “And he said unto me, Unto two thousand and three hundred days; then shall the sanctuary be cleansed” (Daniel 8:14). Heaven replied that the original sanctuary in heaven will be cleansed after 2,300 prophetic days or 2,300 literal years (In Bible prophecy, according to Ezekiel 4:6 and Numbers 14:34, there is a day-for-a-year principle).
After the 70 weeks’ prophecy, which ended in 34 AD, there were remaining 1,810 years (2,300 minus 490 = 1,810). The prophecy ended in 1844 (A.D. 34 + 1810 = 1844). The angel said that at that time, God will clean the heavenly sanctuary (the earthly Jewish sanctuary was destroyed by Rome in A.D. 70). In 1844, Jesus, our high priest in heaven (Hebrews 4:14-16; 8:1-5), began removing the records of sin from the heavenly sanctuary (Revelation 20:12; Acts 3:19-21).
A misunderstanding
In 1833, the Millerites (William Miller) first shared publicly the belief that the Second Advent of Jesus would take place in 1844. They misinterpreted the cleansing of the sanctuary (Daniel 8:14) to mean the cleansing of the earth by Jesus’ second coming. But after their “Great Disappointment” when Christ did not come, those who awaited Christ further studied the prophecies. And they learned that the event reached in prophecy was actually the cleansing of the heavenly sanctuary not the earthly one.
The Bible reveals that there is a sanctuary in heaven (Hebrews 8), which is the original and true tabernacle that the Lord set up and not man. There, Christ ministers on the believers’ behalf, making available to them the benefits of His atoning sacrifice. For at Christ’s ascension, the Father initiated His Son as the great High Priest. Thus, in 1844, at the end of the prophetic period of 2300 days, Christ entered the second and last phase of His atoning ministry.
The investigative judgment typifies the Day of Atonement
The work of the investigative judgment is part of the eradication of all sin. And this is typified by the cleansing of the ancient Hebrew sanctuary on the Day of Atonement (Leviticus 16; 23). In that service, the priests cleaned the sanctuary with the blood of animal sacrifices. However, the heavenly things are cleansed with the perfect sacrifice of the blood of Jesus (Hebrews 7:27; Hebrews 10:1-12).
The investigative judgment reveals who among the dead that are asleep in Christ are worthy to be resurrected. And it also reveals the faithful living that are keeping the commandments of God and the faith of Jesus, and, therefore, are ready to be taken to heaven (Revelation 14:12).
Thus, this judgment vindicates God’s justice in saving those who believe in His Son. It declares that those who have remained loyal to God shall receive eternal life. And at the end of this ministry, Christ will mark the close of human probation before the Second Advent (Hebrews 8:1-5; 4:14-16; 9:11-28; 10:19-22; 1:3; 2:16, 17; Daniel 7:9-27; 8:13, 14; 9:24-27; Numbers 14:34; Ezekiel 4:6; Leviticus 16; Revelation 14:6, 7; 20:12; 14:12; 22:12).

For more info, check: A Great Prophetic Period
In His service,
BibleAsk Team