The sun shall be turned into darkness - See the notes on Matthew 24:29. The same images used here with reference to the sun and moon are used also there: They occur not infrequently, Mark 13:24; 2-Peter 3:7-10. The shining of the sun is an emblem of prosperity; the withdrawing, the eclipse, or the setting of the sun is an emblem of calamity, and is often thus need in the Scriptures, Isaiah 60:20; Jeremiah 15:9; Ezekiel 32:7; Amos 8:9; Revelation 6:12; Revelation 8:12; Revelation 9:2; Revelation 16:8. To say that the sun is darkened, or turned into darkness, is an image of calamity, and especially of the calamities of war, when the smoke of burning cities rises to heaven and obscures his light. This is not, therefore, to be taken literally, nor does it afford any indication of what will be at the end of the world in regard to the sun.
The moon into blood - The word "blood" here means that obscure, sanguinary color which the moon has when the atmosphere is filled with smoke and vapor, and especially the lurid and alarming appearance which it assumes when smoke and flames are thrown up by earthquakes and fiery eruptions, Revelation 6:12, "And I beheld when he had opened the sixth seal, and lo, there was a great earthquake, and the sun became black as sackcloth of hair, and the moon became as blood," Revelation 8:8. In this place it denotes great calamities. The figures used are indicative of wars, and conflagrations, and earthquakes. As these things are Matt. 24 applied to the destruction of Jerusalem; as they actually occurred previous to that event (see the notes on Matt. 24), it may be supposed that the prophecy in Joel had an immediate reference to that. The meaning of the quotation by Peter in this place therefore is, that what occurred on the day of Pentecost was the beginning of the serges of wonders that was to take place during the times of the Messiah. It is not intimated that those scenes were to close or to be exhausted in that age. They may precede that great day of the Lord which is yet to come in view of the whole earth.
That great and notable day of the Lord - This is called the great day of the Lord, because on that day he will be signally manifested, more impressively and strikingly than on other times. The word "notable," ἐπιφανῆ epiphanē, means "signal, illustrious, distinguished." In Joel the word is "terrible or fearful"; a word applicable to days of calamity, and trial, and judgment. The Greek word here rendered notable is also in the Septuagint frequently used to denote "calamity" or "times of judgment," Deuteronomy 10:21; 2-Samuel 7:23. This will apply to any day in which God signally manifests himself, but particularly to a day when he shall come forth to punish people, as at the destruction of Jerusalem, or at the day of judgment. The meaning is, that those wonders would take place before that distinguished day should arrive when God would come forth in judgment.

The sun shall be turned into darkness, and the moon into blood - These are figurative representations of eclipses, intended most probably to point out the fall of the civil and ecclesiastical state in Judea: see the notes on Matthew 24:29. That the Sun is darkened when a total eclipse takes place, and that the Moon appears of a bloody hue in such circumstances, every person knows.

The sun shall be turned into darkness,.... As at the death of Christ, by a total eclipse of it:
and the moon into blood; as at the opening of the sixth seal, Revelation 6:12.
before that great and notable day of the Lord come; when he shall come in power and great glory, as he did in a few years after this, to take vengeance on the Jews, and destroy their nation, city, and temple; in which there was a display of his greatness, and power, and which was awful and "terrible" to them, as in Joel it is called; see Gill on Matthew 24:29.

The sun shall be turned into darkness. See notes on Matthew 24:29.

The moon shall be turned into blood - A bloody colour: before the day of the Lord - Eminently the last day; though not excluding any other day or season, wherein the Lord shall manifest his glory, in taking vengeance of his adversaries.