In a discourse from April 8, 1843, Joseph Smith was recorded as saying the following about the book of Revelation:
Now I make this declaration, that those things which John saw in heaven, had no allusion to any thing that had been on the earth, because John says
“he saw what was shortly to come to pass” and not what
had <already> transpired. (Joseph Smith, Discourse,
8 April 1843, as Reported by William Clayton–B, p. 3)
Commenting on the significance of this vis-à-vis D&C 77, Nicholas Frederick noted that:
This statement suggests that Joseph came to
understand the seven seals as representing time periods that began, at the
earliest, toward the end of the first century AD. (Nicholas J. Frederick, Section
77 and Book of Revelation Scholarship, Religious Educator 22, no. 2
[2021]: 68 n. 59)
In
other words, Joseph Smith did not understand D&C 77 and/or the seven
seals in the book of Revelation as teaching a 7,000 year old earth.