The "thousand years" starts with the binding of Satan. A spiritual event that cannot be witnessed with one's natural eyes.
The Gospel cannot go forth unless the "strong man" is first bound.
Matthew 12:28-29.
Luke 10:17-20
You will say this hasn't happened because the binding doesn't look like your carnal notions thereof. You think that men are little angels and will live pure, peaceful and perfect little lives if the devil cannot deceive the nations. You don't think they're already corrupt, deceivers of themselves, or driven by their lusts to idolize their bellies.
But, the fact that the Gospel goes forth is the signatory evidence of such binding.
How can one enter into a strong man's house, and spoil his goods, except he first bind the strong man? and then he will spoil his house.
Matthew 16:18
And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
So the binding of Satan has occurred. I'm just taking Christ's words here, and I see it in the fact that the church is being built in the earth.
As the event that John said ushers in the "thousand years" has occurred, then the "thousand years" has been ushered in.