This 1st letter was thought to be written 50-55 A.D. Paul wrote the 2 letter around these dates to help support the 1st letter which he taught some things hard to understand. In Fact, even to this day there is much debate about some things in both 1 & 2 Thessalonians. he wrote about in his 1st letter. It was for this reason Paul wrote this 2nd letter to help straighten out some confusion among the church