Matthew 24:39
And the people [i.e., of Noah's day] did not know [when it would happen] until the Flood came and swept them all away. It will be the same way when the presence of the Son of man [arrives].
Matthew 24:50
that slave's master will return on a day that he least expects, and at an unknown hour.
1 Thessalonians 5:1-3
Now brothers, you do not need to have anything written to you about the times and dates [i.e., of Christ's second coming],
2 Peter 2:3
And through greedy desires and deceptive words they will exploit you [for evil purposes]. But the judgment that they have had coming for a long time, will not delay, but will eventually awaken [i.e., arrive] to bring destruction upon them.