Isaiah prophesied the darkening of all three of these sources of light during the Day of the LORD:
Behold, the day of the Lord comes, cruel, with both wrath and fierce anger, to lay the land desolate; and He will destroy its sinners from it. For the stars of heaven and their constellations will not give their light; the sun will be darkened in its going forth, and the moon will not cause its light to shine. (Isa. Isa. 13:9-10) [emphasis added]In Joels vision of the Day of the Lord, the darkening of these same heavenly bodies attends the advance of His army (Joel Joel 2:10-11), which are probably the demonic forces unleashed in the next chapter. The darkening of the sun, moon, and stars will be relatively frequent during the various judgments of this terrible period (Joel Joel 3:15).
The sun became black as sackcloth as a result of the sixth seal judgment (Rev. Rev. 6:12+). During the plagues of Egypt God brought complete darkness during the day (Ex. Ex. 10:21-23), but only a partial darkening is described here. The darkening of the sun, moon, and stars at this juncture is most likely due to cloud covereither by smoke or other physical disturbances (Isa. Isa. 5:30; Eze. Eze. 32:6; Zep. Zep. 1:14-15; Rev. Rev. 9:2+). As in Genesis, the language may reflect the perspective of the earth dweller so that cloud or dust could obscure these cosmic bodies. Others assume the sun, moon, and stars themselves are directly affected: Somehow, the visible luminaries in the heavens for a time, maybe a day, maybe several days, slow down their internal reactions in such a way as to reduce their power by a factor of one-third. The day and night, as a result are only two-thirds as bright as normal, even though the skies are completely clear of haze or anything else to obscure the light.1 Although the text does not say that the skies are completely clear , it is certainly within Gods power to tinker with the internal mechanism of solar power since at a later date the suns burning will be intensified (Rev. Rev. 16:8-9+). See also Jeremiah Jer. 4:23-28; Matthew Mat. 24:29; Mark Mark 13:24; Luke Luke 21:25; Acts Acts 2:20. See commentary on Revelation 6:12. See The Plagues of Egypt and the Tribulation.
a third of the day did not shine
The previous description implied the possibility of a continuous reduction in light, possibly due to intervening clouds or dust. Here, the implication is an eclipse or other supernatural phenomena where all light from the sun, moon, and stars is blocked for one-third of the time. It is almost impossible to estimate the means by which God could bring about this phenomena. However it occurs, it will be dramatic and unmistakable in its unnatural origin. How the fractional darkening of the heavenly bodies can produce a reduced duration of daylight, moonlight, and starlight is a puzzle (Swete). Yet mans ability to grasp the how or the cause and effect is no basis for attributing inconsistency to the author.2