Acts 2:20
The sun will be turned to darkness and the moon to blood before the coming of the great and glorious day of the Lord. — the cosmic darkening (skotia, darkness) and the moon's redness (blood) are standard apocalyptic imagery (cf. Isaiah 13:10, Ezekiel 32:7) signaling the day of the Lord (hemera kyriou) when God judges and redeems. These signs are not merely future; they are inaugurated in the Spirit's outpouring and realized finally at Christ's parousia.