Second Coming
The Second Coming (sometimes called the Second Advent or the Parousia) is a Christian and Islamic belief regarding the future (or past) return of Jesus Christ after his ascension to heaven about two thousand years ago. The idea is based on messianic prophecies and is part of most Christian eschatologies.
William Miller (preacher)
Despite the urging of his supporters, Miller never personally set an exact date for the expected Second Advent. However, in response to their urgings, he did narrow the time-period to sometime in the Jewish year beginning in the Gregorian year 1843, stating: "My principles in brief, are, that Jesus Christ will come again to this earth, cleanse, purify, and take possession of the same, with all the saints, sometime between March 21, 1843, and March 21, 1844." March 21, 1844, passed without incident, and further discussion and study resulted in the brief adoption of a new date (April 18, 1844) based on the Karaite Jewish calendar (as opposed to the Rabbinic calendar). Like the previous date, April 18 passed without Christ's return. Miller responded publicly, writing, "I confess my error, and acknowledge my disappointment; yet I still believe that the day of the Lord is near, even at the door."