Because the feasts belong to God, then they are not meant to simply commemorate events in Israel's history, but they are also closely related to the events involving the Church. They are a pictures of Christ's First Advent, the Church Age, and Christ's Second Advent.
In the Spring Feasts, we find the Gospel clearly presented (1 Cor. 15:1-4)! Passover pictures Christ's death for the sins of the world (1 Cor. 5:7; 1 Jn. 2:2; etc.). The Feast of Unleavened Bread pictures the Bread of Life being sinless (Jn. 6:48; Heb. 4:15; etc.). The Feast of First Fruits pictures Christ's Resurrection from the grave (Acts 26:23; 1 Cor. 15:20, 23; etc.).
The Feast of Weeks, or Pentecost, obviously applies to the Church, in that, the Church began its existence with the indwelling of the Holy Spirit on that day (Jn. 14:17; Acts 2:1-4; etc.). Many students of Bible prophecy, believe that when the "Restrainer" is removed (2 Thes. 2:6-10), the Church will cease to be present on Earth; we will have been taken up into heaven via the Rapture (Jn. 14:1-3; 1 Thes. 4:16-17; etc.).
The Fall Feasts also have to do with the Church Age. For one thing, the Feast of Trumpets (plural) signifies two events: the Rapture of the Church (1 Cor. 15:52 - the last the Church hears; 1 Thes. 4:16; etc.); and the call to Israel to assemble in the Promised Land (Joel 2:1-16; etc.)! Joel says the trumpets are to warn Israel that the "Day of the LORD" is coming. That is also known as the "Day of Atonement" (Lev. 23:27-28), and is referred to as the Tribulation (Dan. 9:27; Mt. 24:21, 29; Rev. 6 - 18). The last of the seven Feasts of the LORD, Tabernacles, will be the Second Coming of Jesus, accompanied by His Church (1 Thes. 3:13; Rev. 19:14; etc.)!
They are His feasts, and all born again believers are invited!