What methods help us figure out when the books of the Bible were written?

from the old testament

• Since Moses wrote Exodus, knowing the dates of his lifetime provides a starting point for determining when the book was written. Moses lived approximately between 1520 and 1400 BC, so the composition of Exodus occurred during that 120-year period. Additionally, Exodus includes information that can further refine the time frame. For example, Exodus 24:4 marks when Moses began to write. Israel’s departure from Egypt occurred when Moses was eighty years old (Exodus 7:7), so he wrote the book of Exodus during the last forty years of his life.
• The Book of Daniel was likely written between 540 and 530 BC, after King Nebuchadnezzar of Babylon had conquered Judah around 605 BC and deported many of its inhabitants to Babylon—Daniel included. Daniel served in the royal court of Nebuchadnezzar and several rulers who followed Nebuchadnezzar (Daniel 1:17–21).

from the new testament

• Second Timothy 3:16–17 assures, "All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be complete, equipped for every good work."
• Paul’s imprisonment in Rome is verified by the book of Acts, where we find references to his being guarded by soldiers (Acts 28:16), being permitted to receive visitors (Acts 28:30), and having opportunities to share the gospel (Acts 28:31). These details, along with Paul’s mention of being with “those of Caesar’s household” (Philippians 4:22), support the view that Paul wrote the prison epistles from Rome, in approximately AD 60—62.

implications for today

Internal evidence for determining when the books of the Bible were written can involve style of writing as well as people, places, and events mentioned in the book. For example, Daniel used Aramaic language in some places and wrote from Babylon, indicating a particular seventy-year period during which the Jews had been deported to Babylon. He also mentioned the exact times when certain kings reigned and which year he recorded certain events to help narrow the time period in which the book was written.

External evidence can also be used to help date when a book was written. For example, all twenty-seven New Testament books were written following the death and resurrection of Jesus, around AD 30—33. The end date of these books also must have taken place by the time of the deaths of the writers. Tradition holds that Revelation was written by the apostle John near the end of the first century. Therefore, external evidence shows all twenty-seven books of the New Testament were composed between AD 30—96.

In some cases, external evidence can help show that one book was written before another without providing the exact time. For example, Luke was likely written just before Acts by the mid-60s and was possibly completed in Rome sometime before the persecution of Christians related to the fires at Rome in AD 64. Sometimes specific books can be determined within a much smaller window of time. For example, Paul’s prison epistles—Ephesians, Philippians, Colossians, and Philemon—were written during the two years he lived under house arrest in Rome, in approximately AD 60—62.

Scholars who believe and affirm the Bible to be God’s inspired, inerrant Word do not always agree on the estimated dates of writing. However, that does not mean the content of the books is in question. A good study Bible such as an ESV or NIV Study Bible or a Bible commentary will lay out the various lines of evidence for the dating of the books.