As a dispensationalist, I recognize the Bible contains seven stages in which God deals with humanity. In each stage, He reveals new information about Himself and His relationship to man. The LORD gives man instructions, man fails to live accordingly, and a new period or era begins. The men through whom God chose to reveal His "new light" were: Adam, Noah, Abraham, Moses, Joshua, Jesus, and the Apostles. The periods, or ages, are identified as: Innocence, Conscience, Human Government; The Land; The Law; The Church; and The Millennium.
Genesis, Exodus, Joshua, the Gospels, Acts, and Revelation present transitions for the people of God. In Genesis alone, there are four dispensations, each with increased revelation and responsibility. It begins with the creation of Adam, and ends with Israel in bondage to Egypt.
Joshua is a transitional book in that it depicts Israel crossing the Jordan River and entering the Promised Land. While there are only three major conflicts with their enemies while Israel wandered through the wilderness for forty years, Joshua is filled with Israel's wars against their enemies.
The Gospels present the Son of God, Jesus, as the promised Christ, the Messiah of Israel. Two verses in John's Gospel sum up what happens (Jn. 1:11-12). Israel rejected their Messiah, and as the result of His death, burial, and resurrection for the sin of man according to the Scriptures, salvation is offered to everyone (1 Cor. 15:1-4; Jn. 3:16; Rom. 10:9-17; 2 Pet. 3:9).
Not all Jews rejected Jesus, and as a result, the Church began on the Day of Pentecost with its membership being entirely composed of Jewish believers. The Book of Acts shows a transition from the Church being made up of only Jews, to the Church including any and all who would accept Jesus Christ, whether they were Jews, Samaritans, or Gentiles (Acts 2:4; 8:5-12; 10:1-48).
The Book of Revelation shows a transition from the Church Age (Rev. 2 - 3), to the Millennial Kingdom of Christ (Rev. 20:1-7), with a seven year period in between known as the Tribulation (Matt. 24:4-28; Rev. 6 - 18), the Time of Jacob's Trouble (Jer. 30:7), and Daniel's Seventieth Week (Dan. 9:24-27). The Church will be gone to be with the Lord (Jn. 14:1-6; 1 Thes. 4:13-18; Rev. 4:1). The Tribulation is God's judgment on the world population, especially Israel, for rejecting His Son.
It is true that God is the same yesterday, today, and forever, but His relationship to mankind has gradually revealed more and more about our unchanging God. Praise Him for revealing Himself to us, and offering us the opportunity to spend eternity with Him!