The covenants of Abraham and Moses were fulfilled in our redemption though Jesus Christ. Those days are fulfilled once more in the middle of the seven years of Tribulation. The Tribulation begins on the 10th of Tishri or the Day of Atonement, so the middle of the tribulation is the 10th of Nisan. On the 10th, the lamb was chosen for Passover so the Antichrist will begin his reign over the world. The two witnesses will be killed on the 14th of Nisan or Passover and resurrect on the 18th of Nisan or Firstfruits.
When they [two witnesses] shall have finished their testimony, the beast that ascends out of the bottomless pit shall make war against them, and shall overcome them, and kill them. And after three days and a half the spirit of life from God entered into them, and they stood upon their feet; and great fear fell upon them which saw them (Revelation 11:7, 11).
Through the Abrahamic covenant, the exodus out of Egypt and the New Covenant in Jesus Christ, we see God's plan fulfilled in God's time. Redemption is completed in Trumpets with His return for His people, Atonement with His return to earth and Tabernacles with His reign on earth. The pattern of God's time helps us understand God's plan for the past and the future.
References: 21st Century Revelation: World Wars, Iraq Wars & End Wars Chapter 10 - Seven Days of God, Chapters 13 - Minor Feast, Major Events, Chapter 16 - The Life of Christ, Chapter 17 - Basic Bible Chronology