1 and 2 Thessalonians are dated primarily based on their greeting from “Paul, Sylvanus, and Timothy” (1 Thess 1:1, 2 Thess 1:1). Sylvanus is another spelling for Silas, who accompanied Paul on his second missionary journey (49-51 A.D.). Timothy also joined the second missionary journey early on (Acts 16:1). However, Silas apparently did not accompany Paul on the third missionary journey, and this trio (Paul, Silas, Timothy) are not mentioned together again. Therefore, the greeting appears to come from the trio some time during their second missionary journey. This would be after they visited Thessalonica and established a church there (Acts 17:1-4). This allows only a very small time window for the letters to be written – from 50 to 51 A.D. This dating of 1 Thessalonians has been widely accepted by scholars of all persuasions with little dissent. For 2 Thessalonians, this date is also generally acknowledged, though there is some dissent.
1 Thess 2:2 supports the timeline in Acts, stating that Paul arrived in Thessalonica after being badly treated in Philippi (he was beaten and jailed – Acts 16:22-24). The reference to Paul’s stay in Athens (1 Thess 3:1) further backs up the sequence of events described in Acts (17:16-34). Therefore, the sequence of events is clear: Paul, Silas and Timothy established a church in Thessalonica, they then traveled to Berea and on to Athens. At this time, Paul and Silas sent Timothy back to check on things (1 Thess 3:2), and after Timothy returned with a report, the trio penned this letter.
Primary opposition to the gospel at this time is described as coming from the Jews, and Paul likens the Thessalonian church to the churches in Judea (1 Thess 2:14-16). This, along with the reference in 2 Thess 2:4 to a standing temple, further confirm a date of writing prior to the A.D. 70 destruction of the temple.