John and Doves,
The day of Christ is the day of the Lord which is 7 years tribulation. I had a post in which I use Zephaniah 2 to demonstrate the day of the Lord = 7 years tribulation.
Philippians 1:6 Being confident of this very thing, that he which hath begun a good work in you will perform it "UNTIL THE DAY OF JESUS CHRIST'.
The day of Jesus Christ = the day of the Lord which is 7 years tribulation. What Paul teaches is this, carry the good work until the day of Christ/ day of the Lord / 7 years tribulation arrives. Simply put, Paul teaches our work stops at the moment the day of Christ/ the day of the Lord/ 7 years tribulation arrives because God calls us home right at the moment day of the Lord begins.
This is another classic example that Paul teaches pretribulation rapture.