{Forget not this one thing} (hen touto m(8820)lanthanet(930a)humas). Rather, "let not this one thing escape you." For
lanthanet(935c) (present active imperative of lanthan(935c)) see verse
 5 . The "one thing" (hen) is explained by the hoti (that)
clause following. Peter applies the language of  Ps 90:4  about
the eternity of God and shortness of human life to "the
impatience of human expectations" (Bigg) about the second coming
of Christ. "The day of judgment is at hand ( 1Pe 4:7 ). It may
come tomorrow; but what is tomorrow? What does God mean by a day?
It may be a thousand years" (Bigg). Precisely the same argument
applies to those who argue for a literal interpretation of the
thousand years in  Re 20:4-6 . It may be a day or a day may be a
thousand years. God's clock (para kuri(9369), beside the Lord) does
not run by our timepieces. The scoffers scoff ignorantly.