Some people teach that Jesus could come at any time because Jesus warned His disciples always to be watchful. While it is true that we do not know exactly when He will come, certain signs of His coming were discussed in my last answer.
Jesus said the coming of the Son of Man will be just like the days of Noah (Matthew 24:37-39). The thing that is striking about the days of Noah is that even in the midst of terrible apostasy, evil, violence and rebellion against God, the people went ahead with their normal lives. They planted fields, they harvested crops, they built houses, they got married, and they had children. They went about business as usual, until the very day that Noah entered the ark, and then destruction came and took them all away.
That is how it will be when Jesus comes again. Business will go on pretty much as usual until the dreadful wrath of God and the Tribulation fall upon the earth. Then it will be too late to turn to God. At that point, Jesus will come back again. He could come back tonight, but some of the signs of His coming–especially the revelation of the “man of sin”–have not yet occurred (see II Thessalonians 2:3).