The Day of the Lord - the Book of Revelation

In the book of Revelation, the last book of the Bible, the end of the world is laid out. And the Day of the Lord, also related to the Day of Wrath, seems to be very upfront when the Sixth Seal is mentioned. 

¹² I looked when He opened the sixth seal, and behold, there was a great earthquake; and the sun became black as sackcloth of hair, and the moon became like blood. ¹³ And the stars of heaven fell to the earth, as a fig tree drops its late figs when it is shaken by a mighty wind. ¹⁴ Then the sky receded as a scroll when it is rolled up, and every mountain and island was moved out of its place. ¹⁵ And the kings of the earth, the great men, the rich men, the commanders, the mighty men, every slave and every free man, hid themselves in the caves and in the rocks of the mountains, ¹⁶ and said to the mountains and rocks, “Fall on us and hide us from the face of Him who sits on the throne and from the wrath of the Lamb! ¹⁷ For the great day of His wrath has come, and who is able to stand?”

This passage has several interesting things in it. First of all the Sun became black as sackcloth, is a very interesting description, if you would have seen the Sun up close - especially when looking at dark spots it looks indeed like sackcloth. But also the moon became like blood. Especially this sign of the Moon divides the start of the Wrath period, while the Sun goes dark and the Moon will not give its light marks the (near) end of the Wrath period. 

God here means business - so to speak - time is up. Because in verse 16 God and Jesus Christ will be seen for all to see. And verse 17 says it all. For the great day... 

So when the Wrath comes all the World will see their Creator but with fierce anger!