There are bible verses that point to a rapture in the future. As for when it will happen, what would be the point of having a rapture in the first place if you go through all the tribulation. The rapture is a form of rescue. Rapturing after the tribulation is over would be like trying to rescue someone who is no longer drowning. It would be pointless. Christians will be raptured aka rescued during the tribulation not before it happens nor after it is over. That's the only thing that makes any logical sense.