1 Thessalonians 5

"For you yourselves know perfectly that the day of the Lord so comes as a thief in the night.  For when they say, “Peace and safety!” then sudden destruction comes upon them, as labor pains upon a pregnant woman. And they shall not escape.  But you, brethren, are not in darkness, so that this Day should overtake you as a thief." vv.2-4

Read chapter 5
Character of the tribulation mentioned here in 1st Thessalonians (not just in Revelation).  The day of the Lord here is not described as what we'd think of heaven but is described as a time of horror.  There are four different "days" in scripture referring to not just a single day but a time with a thing is prominent for example we live in the day of technology.  These four days in scripture are the Day of man (1 Corinthians 4:3) our current situation, Day of Christ (Isaiah 59:19), Day of the Lord (Revelation 1-20), Day of God (Revelation 21-22).
The day of the Lord written here comes with no sign as it comes as a thief in the night, there's no big sign like 2 Timothy 3 signs bringing in the day of Christ, the Kingdom.
Future times is not only in the book of Revelation but in many books in both the old and new testament.  I believe that the day of the Lord, tribulation is not next.  There are multiple things that need to happen before the day of the Lord happens as you compare these other "days."  
So here in 1st Thessalonians we see a sudden destruction, or extermination, when people say "peace and safety."  No one says or thinks we have it today as much as that is what people want and hope for.  Not everyone will be destructed or surprised when the Day of the Lord comes, as those of the light who know and believe Christ will know and understand what's to come.  We are not surprised today of the evil in the world because we know this isn't heaven we're living in now.  Let us not be ignorant either of what is still to come.