The significance of the year 1844 appeared when William Miller headed a movement that was studying the prophecies of Daniel chapter 8 and 9. These prophecies presented the 2300 day prophecy of Daniel 8:14. The Angel Gabriel said, “Unto 2,300 days, then shall the Sanctuary be cleansed.”
The Millerite Christians thought that the Sanctuary was the earth and that God was coming to cleanse it with fire. When we add up the 2,300 years from the commandment to rebuild Jerusalem given in Daniel chapter 9, which took place in 457 B.C., we reach to 1844. So, the Millerites believed that Jesus was coming again in 1844.
And when He didn’t come, some got discouraged, some discontinued studying, and some went back to their respective churches. But, one group that continued studying found out there’s nothing in the Bible that calls the earth the sanctuary. The earthly temple sanctuary was destroyed in 70 AD. So, they understood that the prophecy was referring to the Heavenly Sanctuary because the book of Hebrews tells us that Jesus is now our High Priest in the Heavenly Temple:
“Now of the things which we have spoken this is the sum: We have such an high priest, who is set on the right hand of the throne of the Majesty in the heavens; A minister of the sanctuary, and of the true tabernacle, which the Lord pitched, and not man.” “Who serve unto the example and shadow of heavenly things, as Moses was admonished of God when he was about to make the tabernacle: for, See, saith he, that thou make all things according to the pattern shewed to thee in the mount” (Hebrews 8:1, 2, 5).
And therefore, they understood that in 1844, Christ entered the last phase of that Heavenly Judgment. This special judgment, like that of Israel’s Yom Kippur, represents the final atonement to be made for planet Earth (Leviticus 23:27-29).
For more on this study please check the following link: https://bibleask.org/bible-answers/53-a-great-prophetic-period/
In His service,