“A day is like a thousand years”
With the Lord a day is like a thousand years, and a thousand years are like a day. (2 Peter 3:8 BSB)
What it sounds like today
A nice saying about God being outside of time.
The cultural key
Peter is answering mockers who sneered, 'Where is the promise of his coming? Everything goes on as always.' His reply reaches back to Psalm 90:4, where Moses marvels that a thousand years are to God like yesterday. God does not measure time as impatient humans do; what looks like delay is not forgetfulness or failure but deliberate patience, since (the next verse says) he is 'not wanting anyone to perish.' The verse has also been stretched in later debates over the length of creation's 'days,' a use Peter himself does not make.
Recovered meaning
The seeming slowness of God's promises is patience, not neglect: he keeps time on a scale we cannot feel. To scoffers who mistake mercy's delay for absence, Peter answers that every extra day is room to repent.