Yes, the day is set for Christ to return. But the redemption of Zion is based on the faithfulness of the members.
Joseph Smith said "...could we all come together with one heart and one mind in perfect faith the veil might as well be rent today as next week, or any other time" (Teachings of the Prophet Joseph Smith page 8)
That means we do not so much wait for God to come as God is waiting for us to come to him.
How is that done? It is by keeping all the commandments of God, including those we received in the temple. If being nonjudgmental was the way Zion is built, then there would be no need for the scriptures and their numerous commandments and instruction. But the Lord doesn't work by man's wisdom. Keeping the commandments, paying particular attention to being morally clean, and not neglecting the commandments to save the souls of men, will bring the Holy Ghost into our lives. And that is the only way to build Zion. We become one with each other by all living so we have the Holy Ghost, and the Holy Ghost makes us one both with each other and with the Godhead. No other type of unity can build Zion. No other type of unity is as edifying and pure. As the members as a whole begin to really grow into the Holy Ghost then they will become one in a way that no amount of nonjudgementalism, or "celebrating our differences", or any other worldly model of unity will ever do.
We must keep the commandments, study the scriptures, and save our fellow men. As we do that we are preparing for the second coming. We are preparing by preparing our own hearts for Zion by growing into the gift of the Holy Ghost. And when we have truly done that as a people then we will redeem Zion. What greater preparation for the second coming could we possibly offer?
But we do not "wait" for the second coming. We prepare and work for it.