No one really knows, yet many will tell you that they know. Most evangelicals say, the we will be caught up before a seven year "Tribulation." Others will tell you with equal feeling of certainly that we will rapture 45 days before the "new age" following the seven years to return victoriously with Jesus as "King of Kings." Others with equal certainly will tell you this will happen at three and one-half year into the trib. I would guess the time will be before the "wrath of God" sometime after mid-tribulations (1 Thessalonians 5:9.) Like I said in the opening remark above, NO ONE REALLY KNOWS except God, the Father!
We do know He is returning for His Church. We can read Jesus' own words in the Gospel of Matthew:
"At that time the sign of the Son of Man will appear in the sky and all the nations of the earth will mourn. They will see the Son of Man coming on the clouds of the sky, with power and great glory. … No one knows about that day or hour, not even the angels in heaven, nor the Son, but only the Father." --Matthew 24:30, 36 (NIV)
My theology professor said he was not Pre-, or Mid-, or Post-tribulation but pan-tribulation. If he was still alive today, he would likely add 'pre-wrath." What he did say was: "it would "Pan" out in the end." The oldest theory the end-times seem to be "Post-tribulation" before the 1,000 year reign of our Lord Jesus the Christ. Another Bible teacher says "I have learned to pray for 'Pre-trib. rapture,' and prepare for 'Post-tribulation'." Let's not be myopic, with narrow, nearsighted vision of the future, wasting our time and energy defending our pet theory. Instead live for the Lord, and witness to the wayward person to accept Jesus as their Savior and Lord. Jesus has already paid the price for our sin-nature. We need to humbly repent and accept His gracious gift of forgiveness and the indwelling Holy Spirit.