of that day and hour no one knows

When Jesus said this, he was answering his disciples concerning the timing of the destruction of the Temple, His coming again, and the end of the age:   Now as He sat on the Mount of Olives, the disciples came to Him privately, saying, "Tell us, when will these things be? And what will be the sign of Your coming, and of the end of the age?" Matthew 24:3

So when will these things be?  Jesus said that no one knows the day or hour.  No one knew it when he said this, and no one knows it to this day.  But for those who have ears to hear...this was said in the context of the end of the age and the Second Coming of Christ.  And Jesus spoke of things that would happen, of which he said: when you see all these things, know that it is near—at the doors! Matthew 24:33

We don't know the day or hour now, but we can know it is near, when we see the things of which Jesus spoke.  

Jesus said:

Immediately after the tribulation of those days the sun will be darkened, and the moon will not give its light; the stars will fall from heaven, and the powers of the heavens will be shaken.  Then the sign of the Son of Man will appear in heaven, and then all the tribes of the earth will mourn, and they will see the Son of Man coming on the clouds of heaven with power and great glory.  And He will send His angels with a great sound of a trumpet, and they will gather together His elect from the four winds, from one end of heaven to the other. 

Matthew 24:29-31

And there will be signs in the sun, in the moon, and in the stars; and on the earth distress of nations, with perplexity, the sea and the waves roaring;  men's hearts failing them from fear and the expectation of those things which are coming on the earth, for the powers of the heavens will be shaken.  Then they will see the Son of Man coming in a cloud with power and great glory.  Now when these things begin to happen, look up and lift up your heads, because your redemption draws near.   

Luke 21:25-28

Zechariah, the prophet said:  

It shall come to pass in that day

That there will be no light;

The lights will diminish.

It shall be one day

Which is known to the LORD—

Neither day nor night.

But at evening time it shall happen

That it will be light. 

Zechariah 14:6-7