Three days after William Miller's predicted advent, Joseph reiterated the "eighty-five years old" prophecy and promised that, "There are those of the rising generation who shall not taste death till Christ comes. ... I prophecy in the name of the Lord God, and let it be written, that the Son of Man will not come in the heavens till I am 85 years old, 48 years hence or about 1890." Joseph then indulged in calculations based on biblical prophecy, referring ambiguously to the beginning of the "hour of his judgement" and figuring that if a day with God is 1,000 years, then an hour with God is "41 years, 8 months ..."
[Source: Grunder, Rick, Mormon Parallels: A Bibliographic Source]