the book of revelation describes the day of the lord as an apocalyptic time of god's almighty wrath, which comes upon those who are deemed wicked. the text pictures every man hiding in the rocks of the mountains during a major earthquake to attempt to hide from god's wrath, while celestial phenomena turn the moon blood red and the sun dark. these celestial phenomena are also mentioned in joel 2:31, which foretells the same precise order of events mentioned in revelation: the moon turns blood red and the sun turns dark before the great day of the lord. matthew 24:29-31 mentions the same event, yet it places the celestial phenomenon as occurring after the "tribulation of those days". according to these passages, it then seems that the day of the lord is an event closely tied with the coming of the messiah to judge the world.