D&C 65

In our day, the Lord commands -

"...Prepare ye the way of the Lord, make his paths straight.
2 The keys of the kingdom of God are committed unto man on the earth, and from thence shall the gospel roll forth unto the ends of the earth..."  (Doctrine and Covenants | Section 65:1 - 2)

And then the Lord explains -

"Wherefore, may the kingdom of God go forth, that the kingdom of heaven may come..."  (Doctrine and Covenants | Section 65:6)

It becomes clear that the kingdom of God is the restored Church and the kingdom of heaven is that of the millennium.  In my mind, it also makes clear that the timing of the second coming of the Savior is not a condition of the world's wickedness but that of gathering and preparing the kingdom of God for His return.