The setting of dates by individuals claiming to have knowledge goes against the biblical record. Jesus Himself takes up the topic of His return more than once and His thoughts were recorded in Scripture. Matthew 24 in particular records the Lord's thoughts on the matter. My favorite verse, because it creates a picture that we all can relate to, is 40 and following. In v. 36 Jesus tells the disciples: “But about that day or hour no one knows, not even the angels in heaven, nor the Son, but only the Father." He follows that with this illustration. "Two men will be in the field; one will be taken and the other left. Two women will be grinding with a hand mill; one will be taken and the other left. Therefore keep watch, because you do not know on what day your Lord will come. But understand this: If the owner of the house had known at what time of night the thief was coming, he would have kept watch and would not have let his house be broken into. So you also must be ready, because the Son of Man will come at an hour when you do not expect him." (NIV) Believers must be careful about any teaching that claims to know any specifics about the end times. It appears to this simple Christian that such go against the teachings of our Lord Jesus Christ. Paul writes similarly in 1 Thessalonians 5. I like the image of the thief. If we know when a thief might come, we would be prepared. Since we do not have any idea when--or even if--a thief will come, we prepare as if he could come this day. We lock our door every day, because this might be the day someone tries to turn the knob. So it is with spiritual preparation for Christ's return.
I have trouble thinking of some of the subtle damage this sort of thing will do. People who believed and then witness it not happening will be hurt spiritually, hurt in their faith in ways that are both obvious and subtle. The trust is shattered in so many ways. There is also fear--maybe I am still here because I am not good enough for God? The scrupulous soul may live in anxiety of not measuring up to God's requirements--a position completely opposite to the reality of God's forgiveness and grace.
The Lord's Prayer also rings in my ears: Our Lord taught us to pray in this way, as recorded by Matthew 6:9-13 NIV:
“This, then, is how you should pray:
‘Our Father in heaven,
hallowed be your name,
your kingdom come,
your will be done,
on earth as it is in heaven.
Give us today our daily bread.
And forgive us our debts,
as we also have forgiven our debtors.
And lead us not into temptation,
but deliver us from evil.'"
Note that His Kingdom and His will are to come and be done on earth as in heaven--that's what we are supposed to be praying for! When all the emphasis goes to the hereafter, all too human believers are ready to drop working in this difficult sinful world to help bring it closer to God's Kingdom--becoming all heavenly minded and no earthly good.
While a Christian should not decide to be willfully ignorant about Christ's return, I personally do not find it a compelling issue in my day to day Christian walk. If I ask God daily for the power to live life in a way that is Kingdom-bringing and Kingdom-proclaiming; if I am faithful to follow His will; if I seek to act justly, love mercy and walk humbly with my God (cf. Micah 6:8); if I keep, with God's grace and power enabling me, the two great commandments Jesus gave in Mark 12--to love God with all my heart, soul, mind and strength and second, to love my neighbor as my self. If I do and seek these things, the exact time of the Lord's second coming is not an urgent interest for me. He can come for me tomorrow if He'd like--I'm ready--or He can tarry longer if He wishes. Like Paul, I will press on towards the goal to win the prize for which God has called me heavenward in Christ Jesus. (cf. Philippians 3:12-14 NIV)